Brian Shanahan
Permanoob
Roman sources for the Boii and Insubres of northern Italy (later, Bohemia), two "Celtic" tribes, refer to drugged-up nude warriors called Gaesatae. Standard berserker type story. I dunno if there was a similar Goidelic tradition, but it's not out of the realm of possibility.
You know I'm talking about them courting Dame Palm and her five beautiful daughters before going into battle don't you?