There are many spellings of beaucéant (beauséant, bauceans, and beauçant). There are almost as many etymologies. One page I found offered the one mentioned here as coming from a Provençal word meaning 'piebald': bausan. The word bausan is traced by Meyer-Lübke to the Latin word balteus 'girdle; swordbelt' and whence the English belt.

http://www.crwflags.com/fotw/flags/rord.html#templar

You could try contacting these guys who're writing an online encyclopaedia of the Templars:

http://www.templiers.org/


Ceci n'est pas un seing.