Definition from Wiktionary, the free dictionary
- A blanket placed underneath the saddle of a horse.
- (obsolete, slang) currency in the 1800s consisting of large size notes/bills.
- 1986: William Schneider, Moses Cruikshank, The Life I've Been Living 
- And then he had those great big, what they used to call "horse blankets." You know those bills? Yeah, that's what the young man gave him.
- 2006: BooBooBillQueen, Treasury ordered to make bills recognizable to blind people on Collectors Universe Forums 
- Right now, I am teaching my daughter about "horse blankets" and that "money used to be this big". Who knows? Maybe she will tell her kids how she can remember when dollars didn't have holes for the blind...
- Typically your small size (the same physical size as regular money, as opposed to the old horse blankets) silver certificate is worth about 5% more than face.
- 1986: William Schneider, Moses Cruikshank, The Life I've Been Living