E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A favourite pursuit. The hobby is a falcon trained to fly at pigeons and partridges. As hawks were universal pets in the days of falconry, and hawking the favourite pursuit, it is quite evident how the word hobby got its present meaning. Hobby-horse is a corruption of Hobby-hause (hawk-tossing), or throwing off the hawk from the wrist. Hobby is applied to a little pet riding-horse by the same natural transposition as a mews for hawks is now a place for horses. (French, hobereau, a hawk, a hobby.)