har·ness / ˈhärnis/ • n. a set of straps and fittings by which a horse or other draft animal is fastened to a cart, plow, etc., and is controlled by its driver. ∎  an arrangement of straps for fastening something to a person's body, such as a parachute, or for restraining a young child.• v. [tr.] 1. put a harness on (a horse or other draft animal). ∎  (harness something to) attach a draft animal to (something) by a harness: the horse was harnessed to two long shafts.2. control and make use of (natural resources), esp. to produce energy: attempts to harness solar energy | fig. harnessing the creativity of graduates. PHRASES: in harness (of a horse or other animal) used for driving or draft work. ∎  in the routine of daily work: a man who died in harness far beyond the normal age of retirement. ∎  working closely with someone to achieve something: local and central government should work in harness.DERIVATIVES: har·ness·er n.

harness †baggage, equipment XIII; trappings of a horse; (arch.) body armour; tackle, gear (now techn.) XIV. ME. harnais, herneis — OF. harneis military equipment (mod. harnais) — ON. *hernest ‘provisions for an army’, with assim. of the termination to *-isk- (cf. OF. harneschier equip), f. herr army (see HARRY) + nest = OE., OHG. nest provisions, Goth. ganists safety.
So vb. XIV.