Funny : I searched "cocoon hibernate" on Google and found this page. Ok, it talks about Hibernate, but where is Cocoon ?
It's in the referrers list : someone has hit this page before me by doing the same query as I did, and Google's referrer URL was added to the page and later indexed... by Google ! The snakes bites its own tail ;-)
Update : according to Edmundas' comment, the page used to contain the word "Cocoon" in the list of recently modified pages. This explains the initial indexing. But if you look at Google's cache, it is no more present.
So what happened is that Cocoon appeared once on the page, was indexed by Google, and since then the page is still indexed with "Cocoon" because of the referrer log. So the snake doesn't bite its own tail, but runs after it !!