chum (n.1)
"friend," 1680s, originally university slang for "roommate," from alternative spelling of cham, short for chamber(mate); typical of the late-17c. fondness for clipped words. Among derived forms used 19c. were chumship; chummery "shared bachelor quarters," chummage "system of quartering more than one to a room."
chum (n.2)
"fish bait," 1857, perhaps from Scottish chum "food."