keister
noun /ˈkiːstə(r)/
  /ˈkiːstər/
(North American English, informal)- the part of the body that you sit on屁股 - I’m not going to freeze my keister off out there.我不会在外面冻着我的屁股。 
 词源late 19th cent. (originally referring to a suitcase or box used for carrying possessions or merchandise): of unknown origin.
- I’m not going to freeze my keister off out there.