On the Ball

An early 20th-century American baseball phrase, most likely a shortened form of "keep your eye on the ball," the constant instruction to batters to track the pitch closely. Pitchers who could make a ball do unpredictable things were said to have something "on" it, and the same watchfulness demanded of hitters gave the phrase its wider meaning: someone sharp, alert, and switched on. By the 1930s it had become general figurative slang in America, crossing to Britain by the mid-20th century. Rival theories crediting watchmaker Webb C. Ball or the Greenwich Observatory's time ball have been firmly dismissed by etymologists.