The Collaborative International Dictionary
Harness \Har"ness\ (-n[e^]s), n. [OE. harneis, harnes, OF. harneis, F. harnais, harnois; of Celtic origin; cf. Armor. harnez old iron, armor, W. haiarn iron, Armor. houarn, Ir. iarann, Gael. iarunn. Cf. Iron.]
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Originally, the complete dress, especially in a military sense, of a man or a horse; hence, in general, armor.
At least we'll die with harness on our back.
--Shak. The equipment of a draught or carriage horse, for drawing a wagon, coach, chaise, etc.; gear; tackling.
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The part of a loom comprising the heddles, with their means of support and motion, by which the threads of the warp are alternately raised and depressed for the passage of the shuttle.
To die in harness, to die with armor on; hence, colloquially, to die while actively engaged in work or duty.