on the ball

Example: “The new receptionist is really on the ball.”

Origin: Most plausibly a shortened form of the older baseball instruction "keep your eye on the ball," reduced over time to the punchier "on the ball" while keeping the same sense of sharp, focused attention. By the early 1900s the phrase had broadened well past baseball into general alertness and competence. Two rival, non-sporting theories are also sometimes proposed: one credits Webb C. Ball, a 19th-century watchmaker whose precision railroad timing system helped prevent train collisions, and another points to the Greenwich time-ball, a mechanical device installed in 1833 that visually signaled the exact time to ships in the harbor below. Neither of these alternative stories has the same direct, well-attested support as the baseball connection.