Green’s Dictionary of Slang

snake n.3

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

the penis.

Apollo’s feast: or, Wits entertainment 9: Presently after the English man’s snake grew warm, and crawl’d up the Woman’s Belly, the moving of the bed awakened the Husband.
[US]‘Mae West in “The Hip Flipper”’ [comic strip] in B. Adelman Tijuana Bibles (1997) 90: The taller the bottle the longer the snake / The taller the bimbo / The more she can take.
[Aus]J. Hibberd Dimboola (2000) 87: astrid: He’s nice. Always showing me his pet lizard. mutton: Not to mention his carpet snake.
[UK]P. Theroux Picture Palace 93: She kissed my snake, and I [...] pushed her nice little thighs against my ears like I wanted to drown.
[US]H. Rawson Dict. of Invective (1991) 362: Snake is low slang for the penis, sometimes also referred to as a one-eyed snake.
[US]C. Hiaasen Strip Tease 66: ‘With or without the snake?’ ‘Without [...] Tell her I’ve got one of my own.’.
[US](con. 1986) G. Pelecanos Sweet Forever 252: Had the pistol tucked in his drawers, right up alongside his snake.

In compounds

snakepit (n.)

1. (US gay) a bar frequented by homosexuals.

[US]D.W. Cory Homosexual in America 112: I had been invited to a gay bar that had been nicknamed the snake pit.
[US]B. Rodgers Queens’ Vernacular 186: snake pit 1. den of iniquity 2. dingy, dim-lit gay bar where the brazen clientele frighten straight gawkers.

2. (US) the vagina.

[US]Trimble 5000 Adult Sex Words and Phrases 193: snake-pit (Vulg.) 1. The Vagina.
‘Troy Conway’ Cunning Linguist (1973) 98: [T]he Russian firewater inundated the very inner recesses of her angelic and heavenly snake pit.

3. (US) a prison.

[US]F. Elli Riot (1967) 150: Been in and out of this snakepit for twenty-two years.
[US](con. 1949) J. Hurling Boomers 179: Maggie talked [...] about the awful treatment of mental patients in ‘Snake Pit’.

4. a ‘red–light’ area.

[US]Trimble 5000 Adult Sex Words and Phrases 193: snake-pit (Vulg.) [...] A red-Light District.

5. (also snake ranch) a brothel.

[US]Trimble 5000 Adult Sex Words and Phrases 193: snake-pit (Vulg.) [...] 2. A House of Prostitution.
[US]Maledicta IX 148: The compilers ought to have looked farther afield and found: […] snake pit, snake ranch.

In phrases