mid-15c., from Latin abhorrere "shrink back from, have an aversion for, shudder at," from ab- "away" (see ab-) + horrere "tremble at, shudder," literally "to bristle, be shaggy," from PIE *ghers- "start out, stand out, rise to a point, bristle" (see horror). Related: Abhorred; abhorring.