complete armour, or the whole equipage and accoutrements of a cavalier heavily armed. The word is formed from the French harnois, which some derive from the Greek ἄραξις, 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 harmisch; but others derive it from the Italian arnese, and others from the Celtic harnes, a cuirass.

Harness is also used to signify the furniture put on a horse to draw in a coach or waggon, or other carriage; such as collars, leathers, traces, and so forth.