in [ruby-dev:6289], Shugo Maeda suggested better name for recursive
join error. I, today, happend to had this message and I felt it should
be changed. (maybe too late for 1.6.x)

However, I don't have any good idea, so I decided to ask here.  does
anyone has any idea?

here is one liner to produce the error message.

$ ruby -e "Thread.current.join"
-e:1:in `join': recursive join (ThreadError)
        from -e:1
--
         yashi