Birdie is when a golfer uses one fewer strokes than par to complete a hole. For example, if a golfer completes a par 4 in three strokes, then he/she has made a birdie. Let's now find out why this term is in fact called "birdie."
The term birdie was reportedly invented in 1898 by William P Smith in Atlantic City, New Jersey. Once, when remarking at the shot of a playing partner landing just inches from the hole, Smith exclaimed, "That was a bird of a shot." His playing partner then holed the putt to make one under par on the hole. Word of the term birdie quickly spread among golfers in the United States and Europe, and the word stuck; this word has come to resemble one under par ever since.