Having realised that Mayenne is not really in Normandy though part of it seems to have been at times in the past, I have been looking for a dictionary of Mayennais. and/or Angevin, etc., but still no luck with a translation of "étrages" though it does appear in some definitions in a book on the Internet Archive site : Glossaire des parlers du Bas-Maine (Département de la Mayenne) by Georges Dottin. This one seems appropriate from what I remember of the document I translated which unfortunately I didn't keep:
"étréj", m. pl. : étrages, cours, issues, chemins qui se trouvent devant les bâtiments d'une ferme
In other words yards, ways out, lanes in front of farm buildings.
I seem to remember seeing something about an "enclos" or enclosure too at one point but can't remember where.
The other references in the glossary might be useful to you as you know the lay out of the buildings, yards, etc.
"étyéj" : étrages, jachères which seems to be fallow land
"mani(l)", fumier, engrais f.pl, débris que l'on met à pourrir dans les étrages Cf. fulaj
So the étrages are places where you put debris, probably of vegetation in view of the quote in my previous post, to rot into manure/fertiliser
And fulaj seemes strangely like foulages
"fulaj" : feuilles et débris de paille que l'on met à pourrir dans les étrages, près des bâtiments = leaves and bits of straw you put in the étrages to rot
So presumably nothing to do with the cultivation of hemp or fulling. It would be worth asking local people when you are able to visit.
Judith