Since the questions with these tags have been downvoted by a vast majority of community members, I suggest removing these tags as useless.
I disagree with that. I'll explain why:
language-history or история-языка, is useful because I'm sure users will ask about some historical question. This doesn't mean highly specialized Linguistics questions, but for example, a question like "How did we get to use the expression X?". That's a fine question, I guess.
slavic: This is useful because unavoidably people will ask in questions about Slavic. The problem is when these questions get too specialized or technical. But if you're asking about Russian compared to other languages for some reason, it might be useful.