Context sentences - why?

Another gem:
あさ八じに、はだかではげ山にしゅうごうしましょう。
At 8 am, let’s meet naked on Bald Mountain.

But this gets me wondering. If mt. Fuji is うじさん, why (techically speaking) mt. Bald would be an example for mountain read as やま?
I’m probably misunderstanding things since I don’t know any of the words there ‘-’ “”