Wild and Crazy Heroes!!!
“The Irish were obsessed with war, weapons, and heroics. If their poetry is any indication, they spent most of their time at war with one another, stealing cattle, and feasting on pork.
The Celts scared the Romans and other “civilized” contemporary observers. When they went into battle, they would strip naked and dash at their enemies in nothing but sandals and their fancy necklaces. They howled as if possessed by demons, their shrieks augmented by bagpipes.
Some warriors would be so overcome by battle-frenzy that their very appearance changed. They called this transformation the warp-spasm. The Tain Bo Cuailnge has an excellent description of the hero Cuchulain (or Cu Chulainn) undergoing this phenomenon, which involved most of his body turning itself inside out of his head, after which he killed hundreds of his enemy warriors and walked away unscathed.”
source: The Everything Irish History & Heritage Book