I can remember first hearing one played at a pick-up in a small pub in Ballinskelligs (West Killarney) back in the late 60's so they've been around at least that long and more so in Ireland!
Strangely enough I made my first bodhran from an old wooden riddle or dilurn by removing the mesh and replacing it with parchment. so there is probably some truth in this theory. (saves a lot of buggering about trying to steam wood into a hoop any road!)
I favour the explanation that it originates with Irish kerns banging their pointy sticks on their shields to frighten the enemy