Random House unabridged:
cumshaw - (in Chinese ports) a present; gratuity; tip. [< Chin (Amoy dial.) kam sia,
c. Mandarin kan hsieh
Gosh, the things we learn around here. I certainly had never heard of it, and it's not in NOAD or smaller dictionaries. I agree that it would be helpful to mark it uncommon in LEO.
Even my unabridged dictionary defines it as used in Chinese ports,
which suggests to me that it was sailors' or traders' jargon, not in common currency in the language as a whole.
It would be ideal for the dictionary game or freerice.com (related discussion: Testet Euer Englisch...
), though. (-:
I also thought baksheesh
was a noncount noun, meaning, more or less, money
paid out in, or needed for, small-scale bribes. But it's not a word I would be likely to use myself -- probably just as well.