Thoughts stuck in your head repeating over and over again

[Evisse the Blue]

I always get 'catchy' lines stuck in my head and I chant them stupidly over and over.

First time I read LOTR, I was chanting till exhaustion: One ring to rule them all, one ring to find them ... and in the darkness bind them.

Now, as I'm re-re-reading TTT I found myself chanting :

Seven stars and seven stones
and one white tree

Kinda reminds one of a nursery rhyme, doesn't it?