Definitions
1.VerbTo be friendly toward (with or to) someone, especially in an ingratiating way; to form a friendship (with)."I chummed up with a few of my new work colleagues."
2.VerbTo initiate (a new prisoner) through a ritual involving beating him with sticks and swords, accompanied by music, to extort money from him.
3.VerbTo apply chum to water as bait.
4.VerbTo render a situation frenzied and confusing.
5.Verb↑ John Camden Hotten, A Dictionary of Modern Slang, Cant, and Vulgar Words, London, 1859, p. 21.