Word Origin & History
O.E. hamor, from P.Gmc. *khamur. The O.N. cognate hamarr meant "stone, crag" (it's common in Eng. place names), and suggests an original sense of "tool with a stone head," from PIE *komor- "hammer," from base *akm- "sharp (stone)," cf. Slav. kamy, Rus. kameni "stone." The verb is first attested c.1430.
Hammerhead shark is from 1861.