There is the well known Puranic story of Lord Vishnu taking on the guise of a 'Mohini' to enthrall people both in connection with the churning of the milk-ocean and with the episode of the slaying of Bhasmasura.
In the Bhasmasura story, 'Mohini' towards the end of her dance, persuaded the Asura to place his own finger on his head unwittingly to his own undoing. This episode seems to be picturesquely represented in the first item of the Mohiniyatam called 'Colkkettu' which begins with a pose of the dancer showing with her right hand, the murder of 'Suchimukha' with her first finger pointing to her own head. So Vaishnava devotees could have given the name of Mohiniyattam to this art form
In the Bhasmasura story, 'Mohini' towards the end of her dance, persuaded the Asura to place his own finger on his head unwittingly to his own undoing. This episode seems to be picturesquely represented in the first item of the Mohiniyatam called 'Colkkettu' which begins with a pose of the dancer showing with her right hand, the murder of 'Suchimukha' with her first finger pointing to her own head. So Vaishnava devotees could have given the name of Mohiniyattam to this art form