frighten (or scare) the (living) daylights out of give someone a very severe fright.
☞ This expression was a mid-20th-century development from beat the living daylights out of, on the premise that the effect of extreme fear is as drastic as physical violence.
1955Frank YerbyThe Treasure of Pleasant Valley Didn't mean to hit him…Meant to throw close to him and scare the living daylights out of him.