HARNESS, a complete armour, or the whole equipage and accoutrements of a cavalier heavily armed; as calque, cuirass, &c. The word is formed of the French harnois; which some derive from the Greek ἡρμῶς, "a lamb's skin," because they anciently covered themselves therewith. Du Cange observes, that the word harnesium is used in the corrupt Latin in the same sense, and that it comes from the High Dutch harnas or harnisch. Others derive it from the Italian arnese; others from the Celtic harnes, "a cuirass."
Under king Richard II. it was expressly forbidden all men to ride in harness with lancee-gays. Vide stat. 7 Ric. II. cap. 13. In the statute 2 Hen. VI. cap. 14. harness seems to include all kinds of furniture for offence as well as defence, both of men and horse; as swords, buckles for belts, girdles, &c.