chum
UK[tʃʌm]US[tʃʌm]
n
A close friend.
v
To be or become a close friend of someone.
Etymology
The origin of 'chum' is obscure but it first appeared in English university slang in the late 17th century, meaning 'roommate'. A popular but unproven theory suggests it derives from 'chamber fellow' or the Oxford University term 'chamber mate'. Its journey from specific collegiate jargon to a general term for a close companion exemplifies how informal, closed-group vocabulary can enter the mainstream. The word's concise and friendly sound likely aided its adoption as a casual synonym for 'friend', shedding its original connection to shared lodging.
Analysis
The word 'chum' is a simplex word of uncertain origin, likely arising as a slang term in English. It functions as a single, unanalyzable unit in modern English.
Examples
He's been my best chum since primary school.
They quickly chummed up with the other campers.
I'm going fishing with a few old chums this weekend.