Thiruvathira is celebrated on the star ‘Thiruvathira’ and it falls on a full moon day in the month of ‘Dhanu’-the fifth month in the Malayalam Calendar(Kollavarsham). Festivities of Thiruvathira begin a week before, commencing from Revathi asterism. Women wake up by 4am during the winter season, take their bath and visit nearest Shiva Shrine. On Ardra day, last day of the festive week, wives fast for the welfare of their husband. This encompasses prayers for his life longevity, togetherness, quick reunions or fame of their beloved husband; as the case may be, which would ensure simultaneously long and happy married life. Adherence to Thiruvathira ensures husbands’ well being and in turn, helps maintain marital bliss. Unmarried girls fast on Thiruvathira aspiring for a compatible groom in future. The first Thiruvathira following the marriage of a girl is Poothiruvathira. Celebrations on this occasion are on a grand scale. All members of the family gather at this house for the annual, rather once in a lifetime event of the newly weds.
On Thiruvaathira, the women folk abstain from taking rice and for the lunch a delicious  arrow-root powder  porridge or fruits are served. The women spend the whole  night singing and dancing. Kaikottikkali is an exceptional dance form that is associated with this festival in which a group of women attired in traditional dresses dance in a circle around a lighted brass lamp.
At night, women eat eight different tubers roasted in the fire, which is known as Ettangadi chuduka’ . The night long music and dance is interspersed with a ceremony called Patirappoo choodal, after which, the dance and music continue till sunrise. The festivities conclude with an early morning bath and prayer at the nearby temple.

The Legend
Legend stresses this festival’s association with Shiva-Parvathi union. Sati, the daughter of Daksha Prajaapati had married Shiva against the wishes of her father. . Daksha did not like Lord Siva and was against the marriage of his daughter Dakshayani (Sathi ) to the Lord. Daksha did not invite his daughter and son – in – law for this all important Yaga though everybody else was invited. Lord Siva had tried to dissuade his wife that she would not be welcome at her father's place but the Goddess told the Lord that she would go  there and if she was not treated properly , she would not return. When she came to the yaga place, she was not received but instead Daksha started abusing her husband, the Lord. Unable to bear it, she immolated herself. Enraged at this, Shiva danced the dance of destruction, Sivathandavam, throughout the Universe. The other gods intervened to stop it. Later, engulfed by sorrow, Shiva went to the Himalayas to perform a fierce ‘Tapas’.
The Asura King Taraka started ruling the demons as a good king but later having got two boons from Brahmadeva that he could be killed only by a son of Lord Siva who was seven years old, and that he would be invisible to others, attacked Deva loka and soon conquered the three worlds. The Devas fled heaven and went to Brahma to appeal for help. Brahma suggested that a girl named Sati Paravati would be born to the King Himalaya and his wife Queen Mena and she would be a great devotee of Lord Shiva and would dedicate herself to  Shiva undergoing Thapas to get him as her husband. He asked them to get the help of Kama Deva , the God of Love Inducing him to tempt Lord Shiva, who remains absorbed in His Yoga Samadhi.  Lord Subramanya, the son of Lord Siva and Sri Parvathi, would destroy Tharakasura. As per the request of Indra, the King of Gods, Kamadeva shot his arrow of passion at Shiva, whilst Parvati was placing some flowers in His hands. The moment their hands met, Siva experienced a distracting feeling and fell in love with Parvati . He wondered what it was that disturbed His Yoga. He saw Kama Deva crouching behind the tree. The Lord opened His "third eye", and Kama Deva was burnt to ashes. Siva's seed was thrown into the fire which, unable to retain it, threw it into the Ganges.River Ganges threw it into a reed forest. This is where Lord Subramanya was born; hence, He is called Saravanabhava(born in a reed-forest). He became the leader of the celestial hosts and the destroyer of Taraka as Brahma had ordained. All the women including Kama’s wife Rati started praying for Siva-Parvati union.  After a lot of tests to ensure her genuine devotion to him, Shiva married Parvati on the Thiruvathira day. At the wish of Paravati, Shiva revived Kama to life to delight Rati Devi on the same day. The day on which Kamadevan was burnt by Lord Siva happened to be the Thiruvathira day. As it was on that day the Kama was destroyed, it is commemorated by the ladies every year. It is also the day of celebration of the rebirth of Kamadeva and the union of Siva-Parvathi.

Another legend associated with this festival is that Rugmini followed the fast following Sree Parvati, to become Lord Krishna’s bride. In accordance with Narada’s advice, Gopikas in Vrindavanam also opted for Karthiyayani fast during Spring season. They longed to have Lord Krishna as their husband, made an idol of Goddess Karthiyayani and prayed for a mandala season, which yielded result in merging of their spirits and souls into the Lord on the moon lit night of Thiruvathira. Lord joined them in rasakreeda and with Lord as the centre; they danced on the banks of river Yamuna. Gopikas attained eternal bliss. For this, Gopikas took early baths in river Kalindhi, during the Saraswathi yama; singing hymns and tapping on the water, splashing rhythmically; praising the Lord. They conducted worship with wild flowers, submitted “naivedhyam”with cooked tubers in jaggery, swinging and fasting. All these rituals have later become the customs of Thiruvathira.
Thiruvathira is celebrated also as the birthday of Lord Siva.

The Rituals
Thiruvathira Vratham is initiated by the ‘Ettagadi Chudal’  on the eve of Thiruvathira. Ettangadi refers to an item prepared especially in the evenings of Makayiram. This consists of eight different tubers such as  Chembu, Maranchembu, Chena, Kattukizhangu, Kappa, Koorka, Nanakizhangu and Kaachil or Kavath.There may be regional or local differences in the tubers used according to availability. In the courtyard, on clean land, painted and purified with cow dung slurry, fire is prepared, for roasting tubers. The roasted tubers are peeled, cut into small bits and mixed with jaggery, kalkanda (sugar crystals), honey, ghee, banana bits, nuts, raisins, and sometimes with cooked pulses or dal and scraped coconut. The final mix, after offering to Lord Shiva, Lord Ganesha and Sree Parvathi, is shared by all ladies who are into the fast.  It is specially prepared on occasions of Poothiruvathira. It reminds one of the campfires in a misty moonlit, winter night.
There may have regional and local differences in the way this festival is celebrated, but there is a general form for the observance. Thiruvathira Vrithum also known as Ardra Vrithum starts seven days before Thiruvathira on the star of Revathi . From  that day onwards, women wake up very early in the morning(at Saraswathiyamam), march as a group with lit bronze lamps and “Ashtamangalyam’  to the nearby ponds. After placing the lamps on the bank, they plunge into the pond, form a circle and begin the ritual of ‘Thudikottu’ . One of them takes the lead, singing a song pertaining to Kamadeva. These songs are simultaneously accompanied by Thudi. The palm of the left hand is closed, and kept immediately underneath the surface of the water. Then the palm of the right hand is forcibly brought down in unison in a slanting direction, and struck against its surface so that the water is completely ruffled, and is splashed in all directions producing a deep reverberating sound. This water dance is known as “Thudi”. Since Thiruvathira also commemorates the death of Kamadeva, this hitting the surface of water with an orientation towards the breast is symbolic of breast beating, lamenting the death of Kamadeva. After the bath, the women dress in the neatest and grandest possible attire, preferably in “Settu Mundu”and visit the nearby Shiva temple to offer prayers and to commence their Vrathum.
Early in the morning women drink tender coconut water and eat plantain fruit with a paste made of Ghee and arrowroot powder. Then they , darken their eyes with home made kajal and chew betel leaves to redden their lips. There is a custom of applying Anchukuri on the forehead of married women.  Five lines are drawn in five colors on the forehead.  Red is with sindooram (saffron), chandhanam(sandal paste), yellow with manjal(turmeric), black with the oiled charcoal from Pooja (ganapathy homa kootu) and green made from paste of mukooti leaves(Biophytum).  Breakfast includes an arrowroot pudding (koova payasam) and plantain fruits. Lunch is mostly porridge in wheat or sooji rawa or chama (Panicum milletium) and special Thiruvathira “puzhuku”. Thiruvathira Puzhukku is prepared with eight different tubers, also known as ‘Ettangadi’and some other vegetables. Traditionally, it is prepared with roots such as koorka (Chinese potatoes), Taro (chembu), Sheemachembu, Kaachil, Nanakizhangu, elephant yam (Telinga potatoes), Tapioca, Red beans, horse-gram, Potatoes, raw-bananas, pumpkin, scrapped coconut and garnished with coconut oil and curry leaves.
After lunch women chew betel. There is a convention that each married woman should chew 108 betel leaves. Their husbands may also share this. Then they move as a group for the Oonjalattom (swinging on an oonjal or swing). During this season, huge swings would come up in the backyards of most of the houses on trees.  The swings were made of coir ropes. The seat would be the wide end of a coconut palm leaf stem, cut to the required size. Often, with a strong push, the swing would go so high that the seat and the person on it would veer in another direction and the vines would get intertwined. One would have to go round and round till the swing stopped moving. It was adventure sport of a different kind. Often, it was not confined to sitting but standing on it. Though this swinging is an important item of amusement, it is said that it typifies the attempt these women make in order to hang themselves commemorating the demise of Kamadeva.
In the evening the ladies in the neighbourhood assemble in the central courtyard (Nadumittam) and place a tall bronze lamp (Nilavelakku) and an image of Shiva with some flowers, plantains, coconut and jaggery on a banana leaf as offering to the deity, in the centre. Then begins Thiruvathirakali or Kaikottikkali. They would be neatly attired in a gold-bordered traditional two-piece dress called Mundu and Neriyathu or Settu Mundu. Women also beautifully tie their hair in a form of bun. A fragrant jasmine garland on the bun further enhances the charm of the dancer.  The dance is performed by a group of 7-10 women. They sing and dance to the rhythm of the song also while clapping their hands.  In this one performer sings the first line of the song while the rest repeat it in chorus with clapping their hands in unison. The dance is extremely graceful and requires precise footwork. They dance in a circular pattern around the lamp. The dance depict mainly the Lasya or the beauty element     and to a slight extent the   thandava (dance to destroy the universe) element of dance. The rhythmic movements than mudra are emphasised on in the Kaikottikali. With beautifully coordinated hand movement, the dancers move anti-clockwise first and then clockwise, clapping upwards and downwards in keeping with the beat of the song. The dance is celebration of marital fidelity and the female energy, for that is what brought Kama Deva back to life from ashes, and is performed to gain everlasting marital bliss. The Kaikottikkali  would continue past midnight as women were not supposed to sleep during Thiruvathira night. The dance would be interrupted by "Pathirappochoodal" or the picking and wearing of ‘Dashapushpam’ (Ten sacred flowers) at midnight.  They are Karuka, Krishnakranthi or Vishnukranthi, Thiruthali, Kayyonni or Kanjunni, Mukutti, Nilappana, Valli Uzhinja, Cheroola, Muyalchevi and Poovamkurunilla.These ten sacred flowers are worn along with pathirapoo or the flower of Koduveli. They are worn with an intense remembrance of their husbands. The dance is then continued till early morning when it is stopped for ‘Ardhanareeshwara’ pooja. After this, the women go for bath and prayer in temple. The Thiruvathira Vrithum comes to a finale upon drinking the “Theertham” (holy ablution water).
Thiruvathira is perhaps the only festival that is exclusively meant for the women-folk in India.