Bostin

A cornerstone of Black Country dialect (the industrial area around Dudley, Wolverhampton, and Walsall) used to describe something brilliant or first-rate. One theory connects it to "bursting," in the sense of something so good it's "bursting" with quality, while another ties it to older dialectal senses of "boss," meaning superior or excellent. Both are plausible, and Black Country dialect enthusiasts and linguists alike don't agree on a single confirmed root.