TooMUSH was first designed in October of 1991, mostly due to the fact that people on NarniaMUSH had a disturbing tendency to want to talk about PernMUSH. Advertised shortly thereafter as a Refuge MUSH -- one to go to when your MUD was down, it becam, in general, a good place to talk.
TooMUSH IV has recently graduated from being a small-to-middlin' sized MUSH to a larger one. It often hosts something along the lines of 75+ people at peak times. It is the place players on other MUSHes go when their normal MUSHes go down, currently having refugees from anywhere from X-Men MUSH, to PernMUSH, to PatternFall MUSH.