i just looked it up on wikipedia, this is what they have to say:
“Camp†is derived from the French slang term camper, which means “to pose in an exaggerated fashion.†The OED gives 1909 as the first citation of "camp" in print, with the sense of "ostentatious, exaggerated, affected, theatrical; effeminate or homosexual; pertaining to or characteristic of homosexuals. So as n., ‘camp’ behaviour, mannerisms, etc. (see quot. 1909); a man exhibiting such behaviour." According to the OED, this sense of the word is "etymologically obscure."