Checking the dictionary entries for Eugenius, I was surprised to find different vowel quantities depending on whether it was the adjective or the noun. As you can see from the screenshot above, Gaffiot lists three options:
- Eugĕnĭum: the village of Illyria
- eugĕnīus or -ēus: adjective, ‘of good breed’, referencing Cato’s Dē agricultūrā or Dē rē rūsticā and Varro’s (I presume) Dē rē rūsticā.
- Eugĕnĭus: the male name.
I have no problem understanding why in number two we get a long vowel, given its Greek origin; there are numerous other examples of the same kind of monophthongisation giving long vowels, such as πλατεῖα → platēa. What I am suspecting, is that this is a case of words that happen to look similar, but in fact are of different roots, thus giving the different vowel quantity. Be that the case, then the answer to my question would be ‘both’; be that not the case, then one of the two options are incorrect. Given the precision with which Gaffiot presents the entries, I highly doubt there to be an error, and so would greatly appreciate the input of this community on this: What is the cause of the different vowel length in these entries?
A note: I expect that dictionary entry 2 Eugĕnĭus (entry number 3 in the list) is formed from the place name Eugĕnĭum.