Louis • Link
On the same page, 570, of the L&M Companion's Large Glossary, we have
BEVER: ii.127, beaver, fur hat
BEAVER: ii.203, hat made of beaver's fur or of an imitation of it: 1528
(apparently the earliest OED usage of it in that sense)
JWB • Link
"The initial stage in the hat making process would be the plucking of the coarse guard hairs from the beaver pelt, which was then brushed, with a solution of nitrate of mercury.
This would raise the scales on the fur shafts so that they would become firmly locked together. This process became known as "carotting" and if carried out in a poorly ventilated room, the mercury fumes could damage the brain, hence the expression "mad as a hatter". The fibres would then be cut from the skin and placed on a bench in a workroom known as the "hurdle". Over the bench would be suspended a hatter's bow, very much like an oversized violin bow and the fibres responded to the vibrations of the bow which was controlled by the craftsmen, separating themselves and becoming evenly distributed until they had formed into a thick but loosely structured mat of material known as the "batt". Several batts would then be shaped into a cone and reduced in size by boiling and then rolled to create a firm dense felt. The hood would then be sent onto the hatter who would mould it to the required shape and then line and finish it."
Carolyn • Link
Beaver hats were any hat made of felted beaver fur; they were quite expensive and began to be manufactured in England during the Elizabethan period. The demand for Beaver fur to make felted hats (which looked like a gentleman's silk top hat) was great enough to spur on the American Fur trade (roughly 1620-1850).
Chart showing the number of references in each month of the diary’s entries.