the.com/hitman

means A person hired specifically to kill someone else, usually for money and on someone else's orders.

from A straightforward 20th-century American compound of 'hit' (criminal slang for a planned killing, itself from the general sense of hit meaning to strike or attack) plus 'man.' The slang use of 'hit' for murder shows up in underworld and gangster-era usage, and 'hitman' solidified alongside it as the label for the one who carries the hit out — no hidden story, just crime vocabulary doing exactly what it says on the tin.