We are now up to three wikipedia links and in none of those documents is the phrase "open compound word" used. An "open compound" is a group of distinct words.

We are now up to three wikipedia links and in none of those documents is the phrase "open compound word" used. An "open compound" is a group of distinct words. A "compound word" is a compound made of two more words that have been joined together to make a single word. There is no such thing as an "open compound word". The person you responded to wrote "That is two words or a phrase". You replied "In a word: no. Specifically, it’s a compound word (singular)." In this, the evidence you yourself have provided says you are incorrect. "nominative determinism", if it is a compound at all, is an "open compound", not a "compound word". It is an "open compound", and as such is made up of two words. The person you are refuting is correct. You are correct in identifying it as an open compound. You are incorrect in claiming that it is a single word.