Birdie comes from the American slang 'bird' which meant something wonderful. The term birdie, to describe a score that is one under par for the hole, became widespread in the 1910s. Whereas bogey is a British contribution to the language of golf, birdie is pure American.

Why do they call birdies in golf?

Birdie: In the 19th century, the term "bird" was the equivalent of "cool" or "excellent" - golf scholars believe this is where the term came from. ... Eagle: American in origin, this play on birdie essentially upped the stakes. If a good score of one-under was a bird, a great score of two-under was a more prestigious bird.

Why are eagles called Birdies?

A birdie in golf is 1-under par on a particular hole, an eagle is 2-under par on a hole. Both terms are American in origin, but birdie came before eagle. "Birdie" dates to the first years of the 1900s and to a specific match played at Atlantic City Country Club. Golfer Ab Smith is widely credited with coining the term.