Don't know if it's correct or not, but I always thought that the 3-way's were so named because of their different states when operated. Say for instance that the Common terminal on each 3-way is "A" and the travellers are "B" and "C" then the circuit would have three possible states.
A connected to B on both switches (lights on)
A connected to C on both switches (lights on)
A connected to B on one switch and A connected to C on the other (lights off)
Three states = three way?
If you follow this logic then it could apply to a 4-way switch as well but then that might mean that we would have to start calling regular snap switches a 2-way switch
[This message has been edited by jb (edited 08-24-2003).]