It seems like the biquoques are what we call a grand bascinet, not what we call an armet. Do you agree? Have you seen this term used elsewhere?Item, les aucuns portent différance en harnois de braz, de teste et de jambes ; premièrement la différance du harnoys de teste, cest assavoir de biquoques et de chappeaulx de Montaulban. Et premièrement, les biquoques sont de faczon à que sur la teste, en telle forme et manière come ancienement les bacinez à camail souloient estre, et d'autre part vers les aureilles viennent joindre aval, en telle forme et faczon comme souloient faire les berniers.
Item: Some bear something else for their harness on their arms, head, and legs. First, as for the different kinds of harness for the head, that is to say biquoques and hats of Montauban. And first, the biquoques are of the kind that on the head, in such form and manner as the old bascinet with camail used to be, and from either side opposite the ears they come to join below in front, in such form and fashion as the berniers ("kennel-man, people in charge of the hounds on a hunt"?) are accustomed to make.
We talked about Montauban hats in 2021. I also posted this on the XV century European Armour Facebook group.
Edit: I can see a case that these are armets (the phrase about coming from either ear to join below sounds like hinged cheek pieces) but my understanding is that grand bascinets were common in mid-15th-century France and armets were not, and there is no mention of a wrapper / bevor. So if the author meant what we call armets, he left out a common type of knightly headpiece.
Edit: The FEW volume 21 p. 527a says the etymology is "unknown" and when those old German philologists can't answer something its a good idea to step away slowly.