"Jagoff" (sometimes "jag-off") seems to have originated in Pittsburgh but is also recognized in the Midwest as
slang for an inept, feckless, contemptible, or generally worthless person, a loser, a "schlemiel."
The term is almost certainly derived from the verb "jack off" (through noun "jack-off") as in "masturbate," but somewhat
like the British use of "
wanker," it is usually not a direct comment on self-pleasuring, but more of a general term of contempt or deliberate abuse. Like "
wanker," "jagoff" is somewhat vulgar and not to be used lightly, and avoided in cultivated speech, but is recognized by all in the regions in which it has currency.
.
The
book KILLER CLOWN relates that John Wayne Gacy became especially flustered or
angry when called a "jagoff." So the
police deliberately used that term to throw him off-balance during interrogation.
.