Green’s Dictionary of Slang

1. a general term of abuse.

1939		News Letter and Wasp 23 June 13: The name of the radio character known to thousands, Schlepperman, is evidently a personification of ‘schlep’, which means a poor slob [OED].
1963		T. Pynchon V 104: ‘Quiet, shlep,’ said the doctor, scrubbing.
1968		W. Allen New Yorker 27 July 33: Death was just here. [...] In person. Or somebody who claims to be Death. But, Moe, he’s such a schlep.
2000		Citypages.com 16 Aug. 🌐 Lew Wasserman and Sid Sheinberg [...] took a shine to a 23-year-old schlep from Arizona with one avant-garde short [...] and a lot of moxie to his credit.

2. an ordinary working person.

1998

P. Cornwell Point of Origin (1999) 272: To be honest, it makes the rest of us schleps afraid to be around you, afraid you’ll look at us and disapprove.