Marco Cimarosti scripsit:

> - The sound, /u/, is the same as the sound Greek Upsilon presumably had when
> Cyrillic was invented;

That's the difficulty: upsilon had by that date shifted past /y/ and
was well on its way to /i/, as in Modern Greek. Your other arguments
are cogent, though.

> Finally, old Cyrillic actually had a letter derived from the Omicron+Upsilon
> ligature, called Oku (Unicode U+0478), but it looks very different from
> Cyrillic U, Greek Upsilon and the Omicron+Upsilon ligature.

Indeed. BTW, the reason that Cyrillic "ju" looks like iotated omicron is
that it was originally short for iota-omicron-upsilon.

--
A poetical purist named Cowan [that's me: jcowan@...]
Once put the rest of us dowan. [on xml-dev]
"Your verse would be sweeter http://www.ccil.org/~cowan
If it only had metre http://www.reutershealth.com
And rhymes that didn't force me to frowan." [overpacked line!] --Michael Kay