Origin: 1350–1400; Middle English libertyn < Latin lībertīnus of a freedman (adj.), freedman (noun), equivalent to lībert(us) freedman (apparently by reanalysis of liber-tāsliberty as libert-ās) + -īnus-ine1
late 14c., "an emancipated slave," from L. libertinus "member of a class of freedmen," from libertus "one's freedmen," from liber "free" (see liberal). Sense of "freethinker" is first recorded 1560s, from Fr. libertin (1540s) originally the name given to certain Protestant
sects in France and the Low Countries. Meaning "dissolute or licentious person" first recorded 1590s; the darkening of meaning being perhaps due to misunderstanding of L. libertinus in Acts vi.9.