I ask this, as some fools at the Kingdumb Hell seem to think it is because the "bulletin" refers to weapons of aggression.
It actually originates with the latin BULLA, or notice (hence all the papal BULL). In italian, this became "bulletino" or little notice, fastened to a door or wall.
Somebody in the Witchtower hierarchy is talking a pile of BULL if they really did say it was to avoid reference to weapons...
HB