A small village in the kingdom of Lancre in the Ramtops, mostly known for its funny name and the fact that the world's first female wizard, Esk, was born here (in Equal Rites). The village has a small smithy run by Esk's father, Gordo Smith.
It is also the village watched over by the terrifyingly good (as in capable) witch Granny Weatherwax who has a cottage on the edge of the village.
And since you ask, the name comes from a particularly stubborn donkey. The name may sound crude, but Lancrastians are not ones for senseless niceties.
Another Bad Ass appears in Robert Anton Wilson and Robert Shea's Illuminatus! trilogy of novels. It is a township in Texas which embodies everything the rest of the USA considers a little bit... strange and socially behind the times. Even by the generally understood standards of the Lone Star State of Texas.
"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.