probably from H6972 in the original sense of cutting off; curtailment; Koa, a region of Babylon.
First appearance
Ezek 23:23 The Babylonians, and all the Chaldeans, Pekod, and Shoa, and Koa, and all the Assyrians with them: all of them desirable young men, captains and rulers, great lords and renowned, all of them riding upon horses. (KJV)