Grumpa, I don't know exactly what they were describing, but there are clues. First, they frequently describe the wool leggings as being tied so they are very large and loose about the lower leg. That would minimize the chance of a strike actually contacting your leg, if the legging wasn't actually snug up against the leg. Second, there is a type of fabric advertised for sale at that time which might be similar to that being used. It's called half-thick, and is described as a coarse, thick woolen cloth. There is even one reference to leggings made of it, described as Indian stockings, a runaway.
The Pennsylvania Gazette
April 2, 1741
RUN away .....Had on when he went away, a striped Blanket, brown Duroy Coat, Ozenbrigs Shirt, Leather Breeches, white half thick Indian Stockings, Indian Shoes , worsted Cap, Felt Hat:
I'm guessing, you understand.
Spence