This is the 178th most frequent Bulgarian word.
перник
"Перник" is the name of a city in Bulgaria.
Here, 'ПЕРНИК' again is a proper noun, indicating the hometown of the mentioned friend.
Моят приятел е от Перник.
My friend is from Pernik.
In this sentence, 'ПЕРНИК' is used as a proper noun referring to a city in Bulgaria.
Перник е град в западна България.
Pernik is a city in western Bulgaria.
In this case, 'ПЕРНИК' humorously refers to a stereotype associated with the city or its culture, often used in Bulgarian colloquial language for humor or metaphor.