Why is it called Collie?

The dog breed Collie’s name comes from the Old Scottish words Colley or coaly, which actually means “black.” It could be that these original black-faced sheep are the “black” word from which the collie breeds originally came.
Still, another theory proposes that the Colley sheep, a kind of Scottish sheep, were the ones that these dogs, collies, would normally work with. The dogs were called Collie and later got connected with the breed.