Your first thought is that it's a mispelling. Then you wonder how to pronounce it.
The website was formed by a group of people interested in solving Michael Stadther's A Treasure's Trove. Several names were thrown around for the new website, but the deliberate mispelling from the Table of Contents won out.
Many pronunciations have been suggested such as:
cthree pronounces it "Tweh-lehv". Although his majestic dictation of this word should not be considered law.