A Cool Word That I Had To Look Up

bailiwick - n.

1. A person's specific area of interest, skill, or authority. See synonyms at field.
2. The office or district of a bailiff.

A sphere of activity, experience, study, or interest: area, arena, circle, department, domain, field, orbit, province, realm, scene, subject, terrain, territory, world. Slang bag.

[Edit to add: The source, New Yorker magazine. The context is here:
Every year or so, the record producer Joe Boyd stops in at Caffe Dante, on MacDougal Street, for a pistachio gelato. It’s a matter less of nostalgia than of taste. “I can only like what I like,” he said the other day, during one of these visits. He was spooning up gelato but talking about music, which is his bailiwick, if it’s anybody’s. “I’ve always had the arrogance to feel that what I liked would still be around in thirty or forty or fifty years, and that what other people liked might not.”]