It was a tool you used to perform a function, like a screwdriver.
Nobody listens, but if you want to know just what screwdriver to use, Mr. Santorum will find you the exact one.
also screw-driver, "tool for driving screws," 1779, from screw (n.) + driver. Meaning "cocktail made from vodka and orange juice" is recorded from 1956. (Screwed/screwy have had a sense of "drunk" since 19c.; cf. slang tight "drunk").