I compiled this list of fictional languages for Huffington Post. There must be lots of others I could have included. One I thought of including was the imaginary dialect of the ‘tell‘ from the movie Mad Max: beyond the Thunderdome, but as it’s the only part of the movie I’ve actually seen, I thought perhaps not.
After this was posted I also remembered the imaginary words, supposedly from the Republic of San Lorenzo, introduced by Kurt Vonnegut in his novel Cat’s Cradle. The words are part of the San Lorenzo religion known as Bokononism. Some of them are rather useful. The word granfalloon, for instance: ‘a proud and meaningless association of human beings.’ (Vonnegut suggests nations, among other examples.)