I have never heard the words "hen" or "dan" spoken, other than as nicknames for Henry and Daniel. Meanwhile, I don't think that the words ani, yon, tun, nth, or dun are all that obscure. I would suggest using the Scrabble dictionary; it is a flawed document in my opinion, and in those of many of my Scrabble-playing friends, but it is at least an agreed-upon source.
A hen is a bird. A dan is a grading in judo. Never heard of the five words you mention, but in my opinion the scrabble dictionary is pretty contrived, full of non-words you can sneak onto a Scrabble board anyway.
I woke up in the middle of the night in horror! I realized that I raise chickens, and say the word "hen" every day! Now I have had coffee and defragmented my brain, so I feel better! Sorry to waste your time with a flawed comment. I agree with you on the Scrabble dictionary, but as I said, at least it is an agreed list. I am a retired English teacher, and was once beaten in Scrabble by an Indonesian woman who barely spoke English--but she had memorized that book! Anyway, as a birder, I say the word "Ani" many times a year. My friend the mathematician says "nth" quite often. "To dun" is to pester somebody who owes you money--used more in Britain than in the US, but still a pretty common word; I heard it often when I worked in a collection agency. A "tun" is a big wine cask; the word appears in "Moby Dick" and elsewhere. "Yon" is rather Shakespearean, but it pops up now and again when people want to say "yonder" in an old-fashioned way.