An Etymological Dictionary of the German Language/Annotated/Veilchen

Veilchen, neuter, ‘violet’ (plant), diminutive of earlier Modern High German Veil, from Middle High German vîel, older viôl, neuter, vîole, feminine. Borrowed in the early Middle High German period from Latin viola (with v equal to f, as in Vers, Käfig, Brief, and Vogt). Compare Italian viola, diminutive violetta, French violette; also to Dutch viool, English violet.