I was in Bologna last week, and a couple of churches had an inscription about their dedication to a saint. To my surprise, they used the word divus instead of sanctus. For example, a church may be dedicated to divus Paulus instead of sanctus Paulus.
Is this typical? Is sanctus in this use as well? I faintly recall so. Is there a difference between these words, or is it just a matter of preference?
Superb question!
Divus is a term used to refer to Roman deities or highly esteemed individuals (e.g. emperors). L&S give some classic Latin quotes, and you can also see books about Divus Augustus, Divus Titus, Divus Claudius, and etc.
Now, as many things in Christianity inherited from Roman customs and language, it seems divos was also used for saints. A partial analysis of this, related specifically to the word divos, seems to be in this pamphlet, published in 1865 in Italian, titled "Sulla deificazione nel senso pagano e nel senso cattolico ... relativi all'uso della voce latina "divus" nell'epigrafia cristiana". This can be translated as "On the deification of the pagan meaning and the catholic meaning ... relative to the use of the Latin term "divus" in christian epigraphy."
Now, I do not know Italian, but some few hints from a quick glance at it:
a famous epigraphist, Stefano Morcelli, wrote "expressly condemning in Christian epigraphy the use of the word divus".
"in this writing we have set out to do with greater clarity those same reasons, for which it seems to us however, the Latin word Divus for "Saint in paradise" is appropriate."
the author refers to an inscription in a certain Church of Saint Francis, stating DIVO FRANCISCO ASSISIATI SACRUM. There are also many churches with such epigraphs (e.g. here (bottom right) and here).
apparently, part of the argument against the use of divus was that Divi is too similar to Dei, and thus it might lead to the indication of the deification of saints to the level of God, a clear heresy.
Now, what can I gather from all this? There were indeed many books in Latin using divus to denote saints (e.g. here, here, and many more here). This might have been a "late" practice (I only found books or inscriptions dated from the second millennium), and might have died out after a debate (reflected in the text above) emerged. Still, more needs to be researched to reach a comprehensive answer.
Based on preliminary research, it seems safe to say that divus - and not sanctus - was the preferred choice in Neo-Latin.
You are not the first person to come up with this observation - sorry to disappoint you:
from Thompson (1997) comments to Erasmus:
Besides confirming (by experience, though) what Pavel and luchonacho say, I can add a couple of ideas:
I was writing this answer as luchonacho's popped up. I think it still adds a nuance, so I chose to finish it anyway, trying not to repeat was he already said.
"Sanctus" is the most common term for a saint, used universally.
"Beatus" used to be a common synonym in Middle Ages, but was slightly broader (it could be used for people venerated but not canonized as saints) and later it became a technical term for the "blessed" - a "lower degree of sanctity" necessary before being proclaimed saint.
I don't know much about "divus", I never saw it except for the title of "Divus Thomas" journal. The word had a pre-Christian meaning somewhat similar to a Catholic "saint". As far as I know, it was popular in some regions only.
I'm not proficient in Latin by any means, neither am I a linguist, but I'd like to give my two cents on the matter.
When I was traveling around Italy, I was a bit confused when I first saw Church inscriptions that used the word "divus" when referring to a saint (here, and here). The only Latin word for saint that I'd heard up until that point was "sanctus", since it is the word that's used in the Litaniae Sanctorum and in most of the Latin prayers that I was familiar with. Also, in the Roman Missal, I don't recall ever coming across the word "divus" when referring to a Catholic Saint, but the word sanctus is mentioned many times during the Canon Missae, for instance. This means that the word Sanctus was probably the preferred term that was used in the official prayers of the Church.
That being said, I believe that divus was a less precise term that was used in some ecclesiastical circumstances (i.e., Church inscriptions) as an equivalent of Sanctus, probably due to the fact that during the Roman Empire the word divus was not only used for pagan deities, but it was also used as a sign of respect for the emperors. Therefore, it might've been the case that throughout the Middle Ages the term divus was used as a synonym of sanctus and was devoid of its original pagan meaning. Finally, the fact that there wasn't a big controversy over the theological significance of the word "divus" means that the word probably lost its original meaning and most people just considered it to be a word that was entirely separate to the Latin word for God.
Here is an example of the words divus and sanctus being used interchangeably when referring to a Catholic Saint. Also, this might be a coincidence, but most of the times when I saw the term divus being used, it was connected to the name Francis (i.e., Divus Franciscus, Divus Franciscus Salesius, Divo Francisco a Paula, etc.).
