Please consider this post a 1-man rambling session.
야(夜) means "night," and 심(深) means "deep." That means 야(夜) is a noun, and 심(深) is an adjective. My dictionary says that 야심하다 means "late at night," and 심야 means "the dead of night" or "the middle of the night." Both words seem to mean about the same thing in English, but notice that 하다 is attached to 야심, but not to 심야. Maybe that is because 야심 is a "noun-adjective" combination, but 심야 is an "adjective-noun" combination?
As I mentioned above, 야(夜) is a noun, and 심(深) is an adjective. When the noun comes before the adjective in Chinese writing (한문: 漢文), that usually means that the noun is acting as the subject of the sentence, and the adjective is acting as the predicate. Since 야(夜) is the noun and 심(深) is the adjective, 야심(夜深) means "The night is deep." In the case of 심야(深夜), the adjective comes before the noun, which means that the adjective is just describing the noun, so 심야(深夜) means "deep night." That would imply that 야심 is a sentence, but 심야 is just a modified noun. Maybe Koreans added 하다 to 야심 to show that it is a complete sentence in Korean? Therefore, 야심하다 means "The night is deep." To make 심야 into a complete sentence in Korean, they would have to add 이다. 심야(深夜)이다 would mean "It is a deep night."
I just came across the word 개화(開花)하다, which meaning "blooming" or "bursting into bloom." 개(開) means "to open," and 화(花) means "flower," which means 개화 literally translates as "open flower." My Korean-Korean dictionary says that 개화 means "꽃이 핌," which I would probably translate as "the blooming of a flower." That means that if you add 하다 to 개화, the meaning would be "do the blooming of the flower," which seems possible. However, instead of "꽃이 핌," I would have thought 개화 would mean 핀꽃 or 피어난 꽃. To get the meaning of "꽃이 핌," it seems like the character order should be 화개, instead of 개화.
Anyway, I had to go back and rewrite this whole post because it was just a bunch of virile male cow excrement.