From Old French compaing, compain, from Late Latin compāniō (nominative form) (compare also Italian compagno), from com- + pānis (literally, with + bread), a word first attested in the Frankish Lex Salica as a translation of a Germanic word, probably Frankish *galaibo, *gahlaibo (“messmate”, literally “with-bread”), from *hlaib (“loaf, bread”). See also compagnon, from the accusative form of the same Late Latin term (compāniōnem), from whence also English companion. The boyfriend meaning is by ellipsis of petit copain.
- (male) friend, chum, mate (UK), pal, buddy
- (informal) boyfriend (boy/man to which one has a romantic attachment)
- “copain” in le Trésor de la langue française informatisé (The Digitized Treasury of the French Language).