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Bad Ass
From Discworld & Pratchett Wiki
A small village in the kingdom of Lancre in the Ramtops, mostly known for its funny name and the fact that Esk was born here (in Equal Rites). It is also the village watched over by the terrifyingly good (as in capable) witch Granny Weatherwax.
And since you ask, the name comes from a particulary stubborn donkey. The name may sound crude, but Lancrastians are not ones for senseless niceties.
Annotation
Another Bad Ass appears in Robert Anton Wilson and Robert Shea's Illuminatus! trilogy of novels.
"Bad Ass" is also a North American slang term for "bad attitude," "impressive," "tough," or, charitably, a stubborn clinging on to old ways of thinking, perceived as a little bit anachronistic by the rest of the country.