AtD -- Chum

[Jasper Fidget]

Chum \Chum\ (ch[u^]m), n. [Perh. a contraction fr. comrade or
   chamber fellow: cf. also AS. cuma a comer, guest.]
   A roommate, especially in a college or university; an old and
   intimate friend.
   [1913 Webster]

Chum \Chum\, v. i. [imp. p. p. {Chummed}; p. pr. & vb. n.
   {Chumming}.]
   To occupy a chamber with another; as, to chum together at
   college. [U. S.]
   [1913 Webster]

Chum \Chum\, n.
   Chopped pieces of fish used as bait. [U. S.]
   [1913 Webster]

I don't presently have OED access, but it seems the sense of chum
meaning "friend" or "pal" is more recent?  What can be made of
definition #3 above when applied to a "Chum of Chance", hey?

Or am I starting this shit too soon?