collaboration (n.)

1830, "act of working together, united labor" (especially in literature or scientific study), from French collaboration, noun of action from past-participle stem of Latin collaborare "work with," from assimilated form of com "with" (see com-) + laborare "to work" (see labor (v.)).

In a bad sense, "traitorous cooperation with an occupying enemy," it is recorded from 1940; earliest references are to the Vichy Government of France. Collaborationist was used disparagingly in socialist jargon from 1922.