In chapter 3 of “letter 149 of Jerome”, de solemnitatibus paschae, the author accepts that different approaches to calculating the date of Easter have been used in the church:
… licet in hoc varietas ecclesiae orta est, aliis sufficere credentibus, ut non in decima quarta cum Judeis Pascha celebrarent, …
… some believing it sufficient that they do not celebrate passover/pascha on the fourteenth with the Jews…
Here “pascha” must be accusative, the object of the verb. So why is this not “pascham”?
The answer seems to be that “pascha” is actually a Greek word, and basically indeclinable, and therefore weird stuff can happen.
In the first place, since it is a noun, and ends with -a, there was a tendency to treat it as a first declension noun, and therefore feminine – nom: pascha, voc: pascha, acc: pascham, gen: paschae, dat: paschae, abl: pascha. As you would. There’s plenty of references to this, apparently.
But on the other hand, sometimes you didn’t. There is, it seems, something called a first declension neuter noun, where the accusative is “pascha”. This is attested in the medieval teaching grammar, the “Ianua” of ps. Donatus. Federica Ciccolella – whom we met recently as the translator of the letters of Procopius of Gaza – produced a study of renaissance efforts to produce a Greek “Donatus”, and although this isn’t what we’re looking at, her book is online and gives the text.
In fact – blessedly – she printed the Latin of the “Ianua” in parallel with four of those different attempts at a Greek text. The referemce is Federica Ciccolella, Donati Graeci: Learning Greek in the Renaissance, Brill (2008), online here, p.271, lines 53-55, in the section on the noun (“de nomine”):
Nominativo hoc Pascha, genitivo huius Paschae, dativo huic Paschae, accusativo hoc Pascha, vocativo o Pascha, ablativo ab hoc Pascha, pluralia non habet.
It’s actually fascinating to the see the old grammatical text:
I find that the Wiktionary article gives tables of three different ways to decline Pascha, part of a category of “Latin neuter nouns in the first declension.” It also gives references to four other modern grammarians.
There is also a fascinating article asking for evidence in Latin StackExchange, Was “Pascha” ever used as a neuter first-declension noun? by “Asteroides”, May 4, 2019. The comments are equally interesting.
Basically it comes down to “what do we find in the Latin texts that have reached us?”
All this is a bit above my schoolboy Latin, but it certainly makes sense of the De solemnitatibus usage, and it is rather interesting to see!