Could clerics shed blood? The example of Bishop Odo

Anyone who played D&D in their youth knows that clerics aren't allowed to shed blood, and thus have to carry maces instead of swords. I always thought that was a ridiculous rule first because it wouldn't work--brain someone with a mace and see just how much blood you get--and second because I failed to see the historical connection. Medieval priests often fought, although technically they were not supposed to take up arms of any kind. So I always wondered where Gygax and Company got this idea.

Perhaps they got it from Bishop Odo, William the Conqueror's half brother. The Bayeux Tapestry, which Odo probably commissioned, shows him riding into battle flourishing a club with the caption, "Hic Odo Eps (Episcopus) Baculu(m) Tenens Confortat Pueros", in English "Here Odo the Bishop holding a club strengthens the boys".

So he may not even have used his club as a weapon, but rather as sort of a command staff like the later swagger stick. But another part of the tapestry shows William the Conqueror with a club. Also, in the age of chainmail a club wasn't such a bad weapon. Not as good as a flail (my personal favorite) and certainly not as good as the later medieval handgonnes, but not a bad choice for someone who has sworn never to take up a sword. Odo led troops in battle on numerous occasions, so he might have discovered how effective a club is firsthand.

The goblinkin in my fantasy novel Roots Run Deep are also saddled with primitive weapons. The ruling humans treat them as second-class citizens and, like any group of oppressors, fear those they oppress. Thus they ban goblins and hobgoblins from using metal weapons. Instead our green friends use mauls, quarterstaves, flint knives, clubs like good old Bishop Odo, and a special fighting stick called a tfaa.