bailiwick

bailiwick \BAY-luh-wik\, noun:

1. A person's specific area of knowledge, authority, interest, skill, or work.
2. The office or district of a bailiff.

I'll give it a try, but this is not my bailiwick.
-- Sue Grafton, 'L' Is for Lawless

He "professed ignorance, as of something outside my bailiwick."
-- Marc Aronson, "Wharton and the House of Scribner: The Novelist as a Pain in the Neck", New York Times, January 2, 1994

Fund-raising was Cliff's bailiwick, anyway, and he seemed to have it in hand.
-- Curt Sampson, The Masters

Bailiwick comes from Middle English baillifwik, from baillif, "bailiff" (ultimately from Latin bajulus, "porter, carrier") + wik, "town," from Old English wic, from Latin vicus, "village."