syntax - Ending sentence with two nouns?

This is from NYTimes:

And again and again, and closer and closer, it returns to a speeding commuter train, a recurrence that artfully foreshadows the story’s nifty repetition compulsion.

How can this sentence end with two nouns? What does “nifty repetition compulsion” mean?

Answer

Yes, this is grammatical. The first noun is acting like an adjective. As Colin notes, you can't always put a noun in a the same position as an adjective bu it does work as 'N N'.

'Cheese casserole' isn't a casserole that happens to have a lot of cheese (which is what is implied by 'cheesy casserole'); somehow 'cheese ' is essential to the casserole that is a 'cheese casserole'.

The official term for this usage of a noun as a modifier is Noun Adjunct.

It is not an Adjectival Noun which is the other direction, an adjective that acts like a noun.