Month names collection / metastudy

[Koen G]

The way I currently see the evidence for each month:

* Mars: standard French, would be very unusual in German
* Aberil: not a standard form, but can be expected in Middle High German. Eggy found several examples.
* May: universal, though German is more likely to have different forms. Not the most useful month name.
* Yong: too rare to say much about it, but the g-ending suggests French. Based on very sparse evidence, the initial "y" may point towards the French-Middle Dutch border. 
* iollet: also too rare, but again the llet-ending points towards French
* augst: hardly found in French, very easy to find in German
* septembre etc: French. As I explained, the "in septembre" forms are red herrings based on the Latin ablative form. Our month names are nominative forms and the absolute standard for French.
* octembre: easy to find in northern French dialects.

Ignoring May, that's 7 months towards French, two towards German. Basically, we have to assume "base language influenced by other language". But the base language is almost certainly a broadly northern form of French. We need Germanic influence for aberil and augst.