E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Dobbin.
A steady old horse, a childs horse. Dobby, a silly old man. Dobbies, house-elves similar to brownies. All these are one and the same word. The dobbies lived in the house, were very thin and shaggy, very kind to servants and children, and did many a little service when people had their hands full.