O.E. undon "to unfasten and open" (a window or door), "to unfasten by releasing from a fixed position," from un- (2) + do. Undone "not accomplished" is recorded from c.1300; sense of "destroyed" is recorded from mid-14c.; the notion is of "to annul something
that was done." Undoing "action of bringing to ruin" is recorded from late 14c.