Unfortunately, in most of the Latin texts, Olivetiis capitalized. I suspect the capitalization was used because such place names were considered proper names. If monte Oliveti were rendered in English, it would be Mount of Olives (being considered a proper place name). More to the point might be the Vulgate Luke 23:37:
erat autem diebus docens in templo noctibus vero exiens morabatur in monte qui vocatur Oliveti
whose English equivalent is:
And in the daytime, he was teaching in the temple: but at night going out, he abode in the mount that is called Olivet.
The inference is that "Oliveti" ("Olivet") was a known place name. What do others think?