If we bring into account the Greek Septuagint, of which at least we think the Torah had been done circa 3rd century BCE, and the rest of the books followed in the subsequent two centuries, there were at least more than a few people who could read Hebrew (and likely speak it) in order to translate it all into Greek. The Dead Sea Scrolls do also show there were Hebrew speakers/writers still around as well by the second century CE.
Furthermore more than likely Hebrew was still spoken by many even in the 1st century CE; search for the following by Randall Buth and Chad Pierce: Hebraisti in Ancient Texts: Does Ἑβραϊστί Ever Mean “Aramaic”?; and the following by Ken Penner: Ancient Names for Hebrew and Aramaic: A Case for Lexical Revision. As a result of these two articles’ conclusions, the New Testament also attests that much of the population (at least in Jerusalem) were able to speak and understand Hebrew.
Here’s a rough outline of a scenario I invite you to knock down: The writers may well have spoken Aramaic as well as Greek (and clearly they were literate in Greek), but they did not speak Hebrew and would not have been able to read it.
Does that satisfy the evidence, or am I extrapolating too much from the apparent situation with the gospels?
I sort of answer this above. Quite a few of the names I put in the previous post were taken from the Septuagint, and don’t feature in the Gospels (only the first 3 examples feature in the New Testament); Δαυιδ was present in the Septuagint long before the Gospels were written, thus the same spelling has come from one to the other, where those who did the transliteration were Hebrew readers/speakers.
Sorry this goes so much wider than your concern with υ/ου. It was your assumption of transliteration from Hebrew that got me wondering. Are you perhaps underestimating the oral?
Depends on exactly what is envisioned by the word “transliteration”? For me this isn’t just letter-to-letter correspondence, but also very much includes how the word was pronounced, especially when it comes to Hebrew where there is technically in most names no actual vowel letter used, yet is still provided in the transliteration.
Δαυιδ is a good example of this, where the first α isn’t represented by any Hebrew letter, and in the defective spelling (which was the predominant to the plene) where the ι also isn’t represented by any Hebrew letter. Μυωσης as well, with υω not being a transliteration of any letter in the name. Evidently the pronunciation of the names has to have accounted for the vowel-choices used to represent the vowel-sounds where there’s no underlying letter. The vowel points on Hebrew are a later invention to assist with a pronunciation which was not widely spoken; but this doesn’t matter for pre-3rd century CE, where there were still many Hebrew speakers around (not to mention translators; Aquila, Symmachus and Theodotion were all Hebrew-Greek translators of the 2nd century CE; Hebrew and Hebrew pronunciation will have to have been alive and well for this to be done).
For Hebrew-Greek transliteration (and Aramaic-Greek transliteration), the oral/pronunciation of the word and/or name plays a significant part in how it’s transliterated, whether that be Greek, Latin, or English. How much Aramaic played a part on the pronunciation of Hebrew would be another discussion entirely. 