colter

auran terä A knife or cutter attached to the beam of a plow to cut the sward, in advance of the plowshare and moldboard.
1596, (w), The Faerie Queene, VI.9:

I lately left a furrow, one or twayne, / Unplough'd, the which my coulter hath not cleft ….

What is it but a servitude like that impos'd by the Philistims, not to be allow'd the sharpning of our own axes and coulters, but we must repair from all quarters to twenty licencing forges.