The headword, a diminutive of the gloss, occurs in Aristophanes, Ecclesiazusae 1058, where it is addressed by a hag to the young man she is endeavouring to seduce (web address 1). LSJ understand it 'as a term of endearment, darling', following several Aristophanic commentators in doing so; however, its sense in this content is more faint-heart than sweetheart (cf. Ussher ad loc.).