Dekapentaugousto

[pne]

Also known as, the day when Athens is empty since all Greeks are back in their ancestral village visiting their families.

Also known as Mariä Himmelfahrt, complete with Latin genitive, and in English as Dormition of the Theotokos or Assumption of Mary.

Comments

[pne.livejournal.com]

I've no idea how widespread the practice is; I doubt that this spelling convention is used when learning Latin in Germany, and that it's only in fossilised words and phrases that are considered "German" even if they have Latin inflections -- mostly ecclesiastical and mostly genitive.

Other examples of Latin inflections that come to mind are "Jesu Christi", "Johanni = Johannistag"/"Johannis(kraut)", "Petri(kirche)", and "St. Pauli".