Green’s Dictionary of Slang

schnitzel n.

1. a term of abuse.

1953

G. Marx letter 16 Oct. in Groucho Letters (1967) 95: She is going to appear as Gregory Ratoff’s wife in some schnitzel they are planning to shoot in Egypt [...] The girl prefers a bit part in a B movie in Egypt to New York with the man she loves.

2. the penis.

1966		Trimble 5000 Adult Sex Words and Phrases.
1978		L. Kramer Faggots 321: Think schnitzel, schwantz, sewing machine, slug, spout, sword, tom-tom, wand, wang, water pistol, weener, wienie!, wheezer!, wishbone!, worm!, Ying-Yang!
2000		C. Cook Robbers (2001) 25: Goosing him, stirry that old goood thang. Three alarm schnitzel alert.

In phrases

dip the schnitzel (v.)

(US) of a man, to have sexual intercourse.

2002

J. Ellroy in Crime Time mag. No. 28 Oct. 🌐 Parenthetically, he [i.e. Robert Kennedy] did not play bury the brisket and pour the pork with Marilyn Monroe. He did not dip the schnitzel with her.