keister

[kee-ster] /ˈki stər/
noun, Slang.
1.
the buttocks; rump.
Also, keester.
Origin
1880-85; earlier, as underworld argot, handbag, suitcase, safe; of obscure origin, but words meaning “chest, box” are frequently adduced as sources, e.g., kist1, German Kiste, Yiddish kestl, etc.
British Dictionary definitions for keister

keister

/ˈkiːstə/
noun (slang, mainly US)
1.
the rump; buttocks
2.
a suitcase, trunk, or box
Word Origin
C20: of uncertain origin
Word Origin and History for keister
n.

"buttocks," 1931, perhaps transferred from underworld meaning "safe, strongbox" (1914), earlier "a burglar's toolkit that can be locked" (1881); probably from British dialect kist (northern form of chest) or its German cognate Kiste "chest, box." The connection may be via pickpocket slang sense of "rear trouser pocket" (1930s).

Slang definitions & phrases for keister

keister

noun
  1. The buttocks; rump; ass: I've had it up to my keister with these leaks/What a sensation; we'll knock them on their keister (1931+)
  2. A rear trousers pocket (1930s+ Pickpockets)
  3. A suitcase that opens into a display of goods: the typical ''keister'' of the street hawker (1930s+ Hawkers)
  4. A safe; strongbox; crib (1914+ Underworld)

[fr British dialect kist or German Kiste, ''chest, box,'' transferred to the buttocks perhaps by the pickpocket sense or by the notion that something may be concealed in the rectum]