I've had repetive thoughts like this only it was more about english grammar than it was words, it always happens to me when I take too much of my Inveaga.
I have the same thing, and usually it's at its worst during mania. I say 'worst' because it's really distracting, and the words are so loud and repetitive that it almost physically hurts. Sometimes it's a sentence, or a few words, or just one, but it morphs into other words and the sound sometimes gets distorted... it's very weird. I usually have to say it all out loud to get it under control. I do the rhyming thing too, which can make for some really fun and witty conversations and writing, but it also apparently can come off as being weird at times. I've talked many a person's ear off about the wonderful subtleties of words and sounds... but then I sometimes haven't been able to concentrate on whatever conversation follows because I'm too consumed by the words that are still echoing.
I also have this with music, or at least I recently have experienced it. It can sometimes be pleasant, but it can also get so loud and quickly changing that it's just overwhelming. During these periods I tend to dream of music and then wake up with that in my head, which is actually kind of cool.
Yes, I have words that I consider "comfort words." Like comfort food, they just are soothing. My word is the word "Muffin" That uff sound just is soothing to me for some reason. It's very weird. I don't know if it is a bipolar thing or not, though.
Well from what I remember (i'm far to down to even think i'm capable of mania) when I am manic I will view every word that exists my mouth as beautiful and poetic. So therefore I will in turn adjust my speech to be as poetic as possible. One day actually, I looked up unusual words that began with "S" I believe and began obsessing over each word because in my mind they all looked so beautiful. For me this was related, so in your case it very well could be..
I've had a similar thing and I thought it was more to do with my OCD but it might just be a human thing. strange is a strange word. and the word shark looks like a shark if you blur your eyes. But yeah I have sort of OCD and I rhyme or repeat words in my head sometimes as sort of a tick I guess. If you say any word enough times it begins to sound really really bizarre. I had this happen with the word "modulate."
Yeah I think it's just a weird human brain thing that language sometimes seems strange. It's the medium for communication but it's weird in itself. Does that not make any sense?
Sort of like canvas as art, talking about and thinking about words makes them not just tools for conveying ideas but ideas themselves.
ok I'm going to stop rambling now. sorry