Green’s Dictionary of Slang

schnickel n.

the penis.

c.1904		A. Crowley Snowdrops from a Curate’s Garden 28: From his dripping schnickel frothed a hot stiff stream of greenish piss at an incalculable pace.
1961		T. Taylor Baron’s Court All Change (2011) 95: [T]here’s no difference between their son and myself except I haven’t had my schnickel cut.