galls: chafes. kibe: chilblain on the heel. A chilbain is a painful and dangerous inflammation caused by exposure of the hands or feet to moisture and cold. Hamlet's expression, "galls his kibe," is equivalent to the current (C.E. 2015) expressions, "picks at his sore spot" or "pushes his buttons." A courtier would be proud of his wit, but this gravedigger, a peasant, is wittier than Hamlet, a prince.