Meaning

noun the fleshy part of the human body that you sit on

noun a tooth situated at the back of the mouth

adjective located at or near or behind a part or near the end of a structure

originEtymology tree Proto-Indo-European *pós Proto-Indo-European *-ti Proto-Indo-European *pósti Proto-Italic *posti Old Latin poste Latin post Latin posterus Latin posteriorbor. English posterior Borrowed from Latin posterior (“that comes or follows after; later, latter”).

Etymology from Wiktionary, CC BY-SA 3.0