from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun A covering of soft downy hairs lying underneath the outer hairs of an animal's coat; an undercoat.
Sorry, no etymologies found.
The soft, luxuriant underhair of these goats is not shorn but combed, giving only a small amount of fiber each year.
A Passion for Knitting Nancy J. Thomas 2002
Upon closer look I noticed that simply her top hair are not dreaded, but only the underhair, which made it look that way.
Picked Pics 2009
Underneath, they have a layer of thick underhair that traps air close to the body.