See (in the definition of "ABARIM") : http://fr.wikisource.org/wiki/Page:Dictionnaire_de_Trévoux,_1771,_I.djvu/34
And its discussion page (in French) : http://fr.wikisource.org/wiki/Discussion_Page:Dictionnaire_de_Trévoux,_1771,_I.djvu/34 In this page (and others in the same book) the Greek ligature/letter is present alone, or with a Greek circonflex above (Latin tilde). Currently the Greek ligature "omicron+upsilon above" is encoded (in the page view) as Latin letter "ou" (U+0222 capital / U+0223 small), and corrected (in the full text view) using non-ligatured omicron+upsilon (but it's impossible to say if this introduced a distinction in the Polytonic Greek language at this epoch, so it's not clear that it's really a ligature or a plain letter). Clearly there does seem to be missing a Greek letter, which should behave exactly like the Latin letter. I can't say if this is a contamination of the Greek script by the Latin script (the book itself is in French), or if finally the ligature was also used in Greek books. I think that such famous authors were knowing Greek enough to have seen the ligature used in pure Greek alone. Philippe.
