sheepskin

sheep +‎ skin

sheepskin (countable and uncountable, plural sheepskins)

1. (uncountable) The skin of a sheep, especially when used to make parchment or in bookbinding.
   • 1891, Outing: Sport, Adventure, Travel, Fiction, volume 17, page 137:

     I confess to having felt a prejudice against sleeping in a bag, more especially a sheepskin bag, which would probably have a muttony odor; but it was pronounced to be the warmest and least cumbersome form of bedding we could have […]

2. (US, countable) A diploma.
   • 1919, Henry Blake Fuller, chapter 32, in Bertram Cope’s Year‎, Chicago: R.F. Seymour, page 302:

     […] he took his sheepskin with a bow and a gesture that extinguished several of his companions;

3. (countable or uncountable) The tanned skin of a sheep with the fleece left on, especially when used for clothing, rugs, etc.

• hide, leather, skin

• goatskin, kidskin, lambskin

• sheepskin effect

• OED