Handamage
From Moped Wiki
Handamage is one person's term for when you over power some hand work you're doing, and slip and cut your hand or some incredibly frustrating thing like that.
Example: Loosening a corroded nut off of a bolt with a slightly improperly sized wrench. You're really cranking on the little fucker, and then your wrench slips off the nut and all your knuckles' skin (after having a brief rendezvous with something inevitably close by and made of metal) decides to take a 1-month vacation. The nut remains on the bolt, with a smugness that no one before or since had realized could come from an inanimate object.