1620s, "to slacken (rope) by pulling in the opposite direction to that in which it is drawn," from over- + haul (v.); originally nautical. The extended sense "examine thoroughly with a view to repairs" (by 1705) is via the notion of "pull rigging apart for examination," which was done by slackening the rope by hauling in the opposite direction to that in which it is pulled in hoisting. From 1793 it replaced overhale (1530s) in sense of "overtake," probably by similarity of sound and loss of the literal sense of hale (v.). Related: Overhauled; overhauling.
updated on December 07, 2019