month names

[Anton]

So do/did any Germanic dialects actually say "Septembre"? Or should this be seen as a writing convention (borrowed from Romance) akin to British English "centre"?

Edit: this is important because in the latter case you are essentially arguing that a Germanic speaker wrote a Romance form.

Well, as long as in the VMS we are dealing with writing exclusively, this question, though interesting per se, is not actually essential. Insofar it's been shown with an example that a Germanic person uses -er and -re interchangeably, this suggests that that might have been the case with the VMS as well. This allows one hypothesizing to withdraw the alleged step of the VMS travelling to e.g. some Occitan region (or, alternatively, an Occitan person traveling to the VMS region) from the picture. Because the learned natives of the VMS region would themselves consider -re and -er as equal choices, at least in writing.