Is it ensure, insure, or assure?
Old English sceotere "one who shoots," agent noun from shoot (v.). As a type of gun from 1812; as a small alcoholic drink, 1971. Shootee is attested from 1837.
To defeat someone; thwart or ruin someone's efforts; BLOW someone OUT OF THE WATER: Woody, who had been flying along, level and smooth, was shot down in flames (1940s+)