Word Origin & History
hump1680s (in hump-backed), from Du. homp "lump," from M.L.G. hump "bump," from P.Gmc. *khump-. Replaced, or perhaps influenced by, O.E. crump. A meaning attested from 1901 is "mound in a railway yard over which cars must be pushed," which may be behind the figurative sense of "critical point of an undertaking"
(1914). The verb meaning "to do the sex act with" is attested from 1785, but the source of this indicates it is an older word. Humpback whale is from 1725.