fundament

 
Pronunciation: /ˈfʌndəm(ə)nt/

noun

  • 1the foundation or basis of something.
  • 2 formal or humorous a person’s buttocks or anus.

Origin:

Middle English (also denoting the base of a building, or the founding of a building or institution): from Old French fondement, from Latin fundamentum, from fundare 'to found'