occupyhistory:

Occupy and occupation first became part of the language of protest in September 1920, when factory workers in Italy held strikes against working conditions. About 600,000 workers took control of the factories, and the movement was known in Italian as l’occupazione delle fabbriche, or “the occupation of the factories.” The earliest evidence in the Oxford English Dictionary for the relevant senses of occupy (“to gain access to and remain in…without authority, as a form of protest”) and occupation (“the action of occupying a work place, public building, etc., as a form of protest”) come from reports of the 1920 Italy protests. Another term for protest-style occupation, the sit-in, has been in use since 1937, though it really took off in the ’60s, along with such spin-offs as the teach-in and the be-in.

Ben Zimmer, “Occupy Word Street” from the Visual Thesaurus. He brought ideas from the post to a recent interview with On the Media