For Hundreds of years, scots working-class people were accompanied by their terriers. The wealthy elite owned almost all the land, and only people with prosperity and high social standing were allowed to own large hunting dogs. Poor people in scotland were only allowed to have small dogs. The game dogs whom these people developed hunted all kinds of creatures, including rabbits, rats, squirrels, otters, badgers, and foxes.
The scots came to Yorkshire county in northern England in the 1800's. to work in the mills and mines. They brought with them their little dogs, who hunted the rats in the factories and became house pets.
Yorkie fanciers came from surviving a hard life, not from books. They were breeding for dogs who were good game ratters. tough little dogs who could keep the vermin at bay. The Waterside Terrier is said to be is an ancestor to the Yorkshire Terrier.
The Yorkshire Terrier in the mid 19th century England wern't quite the same as the Yorkies of today. They were larger weighing approx. 12 lbs. their coats were medium , rather then floor length. Still , they were distinct from other terriers of the time, and you can see the family resemblance in the yorkies today.

History:
the Yorkshire Terrier
by Deborah Wood,&
Wayne hunthausen, DVM .