I was reading up on the latest movie remake of Tristan and Isolde (and drooling over the prospect of James Franco and Rufus Sewell being in the same movie) when I did a double take at the title: Tristan and Isolde?
I always read it as Tristan and Iseult. Googling on both brings back results. Why the two accepted versions?
“Tristan und Isolde” is original German of the opera by Richard Wagner, one of the better know retellings of the stoiry. Among the possible versions of her name are Essylt, Iseult, Isolde, Isolt and Ysolt.
(Any other Buffy fans tickled that Giles answered a literary question first? 
)
As for why, it’s because it’s an old story that’s been told over and over, and spelling changes. For what it’s worth, it’s always pronounced roughly the same: “ee-SZOLT”
It helps that I’m a librarian. But I don’t know anyone called Buffy (at least, not in real life).
Hey, you’ve got Tristan, Tristram, Drustan, etc. for the guy, too. There are plenty of variations.
For what it’s worth, this story is one of the oldest in the Arthurian canon, and they may even have been real people (along with king Mark). Their names show up in ancient inscriptions, in various even weirder spellings.
Isolde is pronounced with three syllables. (When I pronounce it anyway).
I agree with bibliophage and pronounce “Isolde” with 3 syllables: “ee-ZOL-duh.”
That’s the way it’s pronounced in Wagner’s opera, anyway, which is the version I’m most familiar with.
Thanks for the explanations! Isolde, Iseult–anyway you slice it, it looks like it’s gonna be a great movie.
Now I can go back to drooling over two hot men. 
One version that predates Wagner and probably influenced his decision is Gottfried von Straßburg’s Tristan (early 13th century, Middle High German) where the name is spelled Îsolde.
http://www.fh-augsburg.de/~harsch/germanica/Chronologie/13Jh/Gottfried/got_tr00.html
And yes, in a German context - von Straßburg, Wagner… - it is pronounced with three syllables.