The legend of Hartalika Teej originates from a story told by Lord Shiva to Goddess Parvati about her previous incarnation as Shailputri.
Shailputri, the daughter of King Himalayaraj, performed intense penance and austerity for 12 years to please Lord Shiva, followed by another 64 years of devotion.
Worried for his daughter's future, Himalayaraj lied to Shailputri when the sage Narada Muni visited, telling her that Narada had brought a marriage proposal from Lord Vishnu. Himalayaraj promised Narada that Shailputri would marry Lord Vishnu, and Vishnu agreed to the marriage.
Upon hearing of her father's promise, Shailputri was distraught and left home with her friend to live in a cave and continue her penance to Lord Shiva. Pleased by her devotion, Lord Shiva promised to marry Shailputri. The next day, Shailputri and her friend fasted for Lord Shiva on the Shukla Paksha Tritiya day during the Bhadrapada month.
Thinking his daughter was kidnapped, Himalayaraj searched everywhere before finding her in the forest. He requested she return home, but Shailputri agreed only if he would let her marry Lord Shiva. Himalayaraj conceded and later married Shailputri to Lord Shiva.
The story is the origin of the name Hartalika for this holy day, as "Hartal" means abduction and "Aalika" means female friend - referring to Shailputri's friend who took her to the forest. The Teej fast commemorates Shailputri's devotion to Lord Shiva.