- \ \  Tractor is one of a large family of English words that come from tractus, the past participle of Latin trahere ‘pull’ (others include abstract , attract, contract, detract , distract , extract , retract, subtract, trace, tract , tractable , traction , trait, treat, treatise, and treaty). Tractor itself was originally used in English for a device, invented by the 18th-century American doctor Elisha Perkins, for ‘pulling’ across the surface of the skin, which was supposed to relieve rheumatic pains. It was not applied to a ‘vehicle for pulling loads’ until the end of the 19th century.\ \ From Latin trahere itself come English retreat and train; and drag may go back to the same ultimate source.\ \ Cf.⇒ ABSTRACT, ATTRACT, CONTRACT, DETRACT, DISTRACT, EXTRACT, RETRACT, RETREAT, SUBTRACT, TRACE, TRACT, TRAIN, TRAIT, TREAT, TREATY
Word origins - 2ed. J. Ayto. 2005.