fundament
/ˈfʌndəmənt/noun
1
- the foundation or basis of something基础, 根本。
2
- formal or humorous a person's buttocks or anus〈正式或幽默〉（人的）臀部; 肛门。
词源
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'.