Green’s Dictionary of Slang

a contemptible, foolish or immature person, an upstart, a dupe.

1944		M. Samuel Harvest in Desert 115: The colonists called the workers Shmendriks, tatterdemalions, n’er-do-wells [OED].
1951		A. Hirschfeld Show Business is No Business 47: Our hero describes himself [...] as a schmendrick with a noodle for a brain .
1968		‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 51: schmendrick – Handle for the ultimate in clodness.
1990		(con. early 1950s) J. Ellroy L.A. Confidential 449: The shmendriks at the mortuary think they’re burying a midget.
1997–2000		Da Bomb 🌐 25: Shmendrick: Dorky, stupid person.
2004		J. Ellroy ‘Hot-Prowl Rape-O’ in Destination: Morgue! (2004) 275: Danny G. was a marvellous mensch [...] He wasnt a schmendrick, a schlemiel, or a schlimazel.
2004		Mad mag. Oct. 39: Start with Tiffany Shlemendrick of Altoona, PA.
2013		T. Pluck ‘Six Feet Under God’ in Life During Wartime (2018) 189: ‘I’m not a rabbiit, I’m a rabbii, you schmendrick!’.
2021		J. Ellroy Widespread Panic 166: Who’s this Ahlendorf schmendrick?