means A person you share a living space — typically a bedroom, apartment, or house — with, often to split the rent.

from A plain English compound of "room" and "mate," both old workhorse words. "Room" descends from Old English "rūm," meaning space, and "mate" comes from Middle Low German or Middle Dutch "māt," originally a companion you shared food with — built from the same root that gives us "meat" in its old sense of food. So a roommate is literally a space-companion. The term itself is an American coinage that took hold in the 19th century, riding the rise of boarding houses and college dormitories.