Middle English hakeney, prob from Hakeneye Hackney, borough of London, where many horses were formerly pastured. The word orig denoted an ordinary riding horse, later shortened to hack (see hack³ (2c)); such horses were often hired out for riding or driving, hence hackney², hack³ (2a), and hackneyed (from the idea of being used by all and sundry). From the 17th cent. a vehicle available for hire became known as a hackney coach or hackney carriage; the latter is still the official term for a taxi (compare hack³ (4)); this usage prob led to the current sense, the hackney being chiefly used for driving