Beat/scare the living daylights out of someone

From the mid-18th century, ‘daylights’ was slang for ‘the eyes’. ‘To beat/scare the living daylights out of someone’ means either administer a merciless beating or defeat or frighten someone out of their wits. Both expressions date from the late 18th/early 19th century. ‘Living’ is simply an intensifier that means ‘very’ or ‘real’. Henry Fielding in Amelia (1752) wrote, “If the lady says another such word to me, I will darken her daylights” (blacken her eyes).