Nouns can modify nouns: cat food, coffee cup, gold ring, laser surgery, flood insurance. It seems to me there are even cases where a noun sounds better than the corresponding adjective: sociology papers sounds a bit better than sociological papers.
Some noun-noun combinations don’t work. You wouldn't say America gangsters or measurement spoons or greed crimes. If you spilled water on your keyboard you probably wouldn't call it a keyboard spill or even a water spill.
Are there rules that tell which combinations are acceptable?