bougre (Middle English) comes from Old French bougre, from Medieval Latin Bulgarus, from Slavic блъгаринъ, from Old Turkic 𐰉𐰆𐰞𐰍𐰀, from Proto-Turkic bulgar, from Proto-Turkic bulga- — to stir, stir up; to produce a state of disorder.
bougre (Middle English): heretic