It's probably best to think of it as a kind of domain-specific term of art. Same goes for the 'news' in HN's title - the site has about the same relationship to

It's probably best to think of it as a kind of domain-specific term of art. Same goes for the 'news' in HN's title - the site has about the same relationship to 'news' as USENET newsgroups, the city of Newport News or the word 'sinews'.