Green’s Dictionary of Slang

mustard pot n.

1. as a part of the body.

(a) (also mustard bowl, mustard box, mustard-jar, pot) the vagina.

Tell Trothe’s New Yeare’s Gift (1876) 19: She was beetell-browed, goggell-eyed, blobber-lipt, wry-necked, crooke-backt, and splay-footed: havinge the huckle bone of her breech burst, whereby shee wente wriggling with her taile like a broken legged dogge [...] With this unmatchable creature did this stripling marrie, supposing it unpossible that she that had never a good part in her body, shoulde [...] lende his mustard pot others uses.
[UK]Mercurius Fumigosus 22–25 Oct.–1 Nov. 190: A brace of Virgins in Black-Colt Alley [...] holding a Conference one morning to which had the best Mustard-pott.
[UK]J. Ray Proverbs (2nd edn) 86: He’s a Hot shot in a mustard pot, when both his heels stand right up.
[WI]T. Chatterton Revenge I ii: If my courage holds, egad, I’ll strap her: / Thro’ all Olympus shall the thunder roll, / And earth shall echo to the mustard bowl.
[Scot]W. Tennant Anster Fair I xxiii 13: Ne’er smelt a Phoenix-nest so sweet, I wot, / As smelt the luscious fumes of Maggie’s mustard-pot.
[UK]Farmer & Henley Sl. and Its Analogues.
(con. 1900) J. Carpenter Chanties 488: Once I had a wife, / And she was doublejointed; / I thought she had two mustard pots, / But I was disappointed [HDAS].
[US] in P.R. Runkel Law Unto Themselves 258: I’d bend down between her legs [...] and I’d feel my hand up ’er mustard jar. [Ibid.] 259: She didn’t like me t’put my tongue in ’er mustard box.

(b) (US) the anus.

[US]B. Rodgers Queens’ Vernacular 19: the rectal opening, anus [...] mustard pot (’40s–’50s).

2. a carriage with a light yellow body.

[UK]J. Ware Passing Eng. of the Victorian Era.

3. (US prison) a passive homosexual.

[US]V.F. Nelson Prison Days and Nights 149: The passive participants in sodomy are called ‘punks’, ‘gonsils’, ‘mustard pots’, or even more direct physical terms are used.