To finish off the trivia, I believe "ut" and "si" (for the initial letters of Sancti Iohannes) are used in most languages other than English. "Ut" was changed so all the syllables would be a consonant followed by a vowel (same reason the l in "sol" was dropped), and "si" was changed so there wouldn't be two syllables beginning with the same letter. All this was part of an attempt in England to provide some kind of singable musical "notation", especially for people who couldn't read music, I guess.

And by the way, Mary Martin can share some of the credit with Julie Andrews for making it famous. And, I guess, Rodgers and Hammerstein.