Close friends or companions, especially people who spend a lot of time together.
Chum likely comes from 'chamber mate' (roommates), shortened and slurred together in British universities in the 1600s. The word evolved to mean any close friend or companion.
Chum is one of those words that originally referred to shared living spaces, just like 'roommate'—it shows how proximity creates friendship, and English captured that connection in the word itself!
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