1300-50;Middle Englishbougre < Anglo-Frenchbugre < Medieval LatinBulgarus heretic, literally, Bulgarian, by association of the Balkans with heretical sects such as the Bogomils and their alleged deviant sexual practices; def. 1 perhaps by reanalysis as bug1 or bug2 + -er1 (cf. booger)
"sodomite," 1550s, earlier "heretic" (mid-14c.), from M.L. Bulgarus "a Bulgarian" (see Bulgaria), so called from Catholic bigoted notions of the sex lives of Eastern Orthodox Christians or of the sect of heretics that was prominent there 11c.