Actually, its was origionally a group of servers that split of from their hub server. EFnet stands for:
Eris Ffree Network
Obviously, Eris was the server they were breaking away from.
It is the largest IRC Network, boasting about upwards of 40,000 users logged in at a time. Its a shithole...but its a fun shithole. At least it never gets too dull.
At least it isn't...*shudder*..DALnet...