Green’s Dictionary of Slang

snake n.3

[abbr. one-eyed trouser-snake under one-eyed adj.]

[early 18C; 1940s+] the penis.

In compounds

snake charmer (n.)

[1970s+] (US gay) a fellator.

snake gully (n.)

[1960s–70s] the vagina.

snakepit (n.)

1. [1950s–70s] (US gay) a bar frequented by homosexuals.

2. [1960s-70s] (US) the vagina.

3. [1960s] (US) a prison.

4. [1960s] a ‘red–light’ area.

5. [1960s+] (also snake ranch) a brothel.

In phrases

take one’s snake for a gallop (v.) [1940s+]

1. to masturbate.

2. to urinate.