One of the numerous names of the pansy or hearts-ease. Originally white, but changed to a purple colour by the fall of Cupid's bolt upon it.
Yet marked I where the bolt of Cupid fell. It fell upon a little Western flower, Before, milk-white, now purple with love's wound; The maidens call it Love-in-idleness.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894