Now the only thing a gambler needs/Is a suitcase and chum/And
the only time he's really satisfied/Is when he's on the drum

The story:

I imagined that "chum" referred to the money a gambler would
bring with him, to "chum the waters"...and that "on the drum" was
some sort of gambling term for being on a roll, having a streak of
luck. I only realized what it was...today, on this site.