desdar

A rare, mostly archaic verb meaning to unwind a rope, handle, or spool in reverse to undo previous turns, or, in an older and now largely replaced sense, to unfasten clasps or fastenings. It conjugates irregularly, following the same pattern as dar (desdoy, desdi, desdieron).

• Hay que desdar el cordel antes de volver a enrollarlo. — You have to unwind the cord before rolling it back up.
• El marinero desdaba el cabo con cuidado. — The sailor was unwinding the rope carefully.
• Desdio los broches del abrigo con torpeza. — He fumbled the coat's clasps undone.

This is a rare, technical/archaic word most native speakers rarely use — don't reach for it as an everyday synonym for desatar (to untie) or desabrochar (to unbutton), which are what modern speakers actually say.