Peter Giles

“ In Sweet's terminology u (oo) , as pronounced in English “put” or “too,” is a high back wide round, while the sound in the French sou or the Scotch pronunciation of “ book ” is a high back narrow round. The high front corresponding sound is found in the French lune. With this the German “modified u” (ü) is often equated, but it is not really identical, being a mid front narrow round vowel. The pitch of the vowel u is among the lowest of the vowel sounds ”

“ In the Phoenician alphabet T is the last symbol, but there can be little doubt that when the Greeks introduced symbols for vowels, which had not been indicated in the alphabet they had borrowed, they took the sixth symbol of the Phoenician alphabet (see F) in its ordinary formand placed it at the end of the alphabet with the value of a vowel. This vowel was apparently u (English oo in moon) , though Ionic and Attic Greek at a very early period changed it to the sound of the French u. ”

“ In modern English ū preceded by i̯ (y) arises from three different sounds in middle English: (a) the long French u (ü) brought in with borrowed words from French (duke) , (b) ēu (Early English ēow) as in “new,” (c) a more open sound ēu (Early English ēaw) as in “dew” (Sweet, New English Grammar, § 806) . ”