The buttocks; rump.
A satchel, suitcase, etc.
(slang) A suitcase; a satchel.
Origin of keister
- Earlier satchel, suitcase ultimately from German Kiste box, case (also buttocks, anus, in German slang) from Middle High German box, case from Old High German kista from Latin cista chest
From American Heritage Dictionary of the English Language, 5th Edition