Boches :
Old word, very negative, started being used during the 1870 war between french and german.
Comes from "al" for german (allemand in french) and "bosh" for thick head, nut, noodle (caboche, tête de bois in french).
Later condensed as "boche" during first world war, when it was used by the soldiers in the trenches to talk about their german comrades, and not necessarily in a negative way. Was later used more commonly during WWII, as a very negative term, to designate a german person. Not much used since then, except by people who lived during the war.
