1520s, of persons, "fickleness;" 1610s, of things, "mutability, irregularity," from Latin inconstantia "inconstancy, fickleness," abstract noun from inconstans "changeable, inconsistent" (see inconstant).
"moral fault, wickedness," c. 1300, from Old French vice "fault, failing, defect, irregularity, misdemeanor" (12c.), from Latin vitium "defect, offense, blemish, imperfection," in both physical and moral senses (in Medieval Latin also vicium; source also of Italian vezzo "usage, entertainment"), which is of uncertain origin.
Vice squad "special police unit targeting prostitution, narcotics, gambling, etc.," is attested from 1905, American English. Vice anglais "fetish for corporal punishment," literally "the English vice," is attested from 1942, from French. In Old French, the seven deadly sins were les set vices.
Horace and Aristotle have already spoken to us about the virtues of their forefathers and the vices of their own times, and through the centuries, authors have talked the same way. If all this were true, we would be bears today. [Montesquieu, "Pensées"]