See quotation 1832. The word occurs in Blundevil (1580) and in Markham (1607). (N.E.D.)
1796. The favourite gaits which all their horses are taught [in Virginia], are a pace and a wrack.… In the wrack, the horse gallops with his fore feet, and trots with those behind.—Isaac Weld, ‘Travels through North America,’ p. 107 (Lond., 1799).
1816. At Louisa I bought a new horse,—one of your capital racking ponies, as they are yclept.—J. K. Paulding, ‘Letters from the South,’ i. 103 (N.Y.). (Italics in the original.)
1817. They [the horses] generally pace, or “rack,” as it is called, being taught that mode of going in their breaking.—M. Birkbeck, ‘Journey in America,’ p. 61 (Phila.).
1832. The Americans who have spoken to me about riding say that they do not like a horse to have what we consider proper paces, but prefer a shambling sort of half-trot, half-canter, which they judiciously call a rack, and which is the ugliest pace to behold, and the most difficult to endure, possible.—Frances A. Kemble, ‘Girlhood,’ iii. 257. (N.E.D.)
1845. See Appendix II.
1888. He [the horse] is very affectionate, and he racks a mile inside of three minutes.—Mrs. Custer, ‘Tenting on the Plains,’ p. 187
