In golf, why do they use the...

The slang word birdie originated in 1899, when, according to a story by Ab Smith, “… my ball … came to rest within six inches of the cup. I said, ‘That was a bird of a shot… . I suggest that when one of us plays a hole in one under par, he receives double compensation.’ The other two agreed and we began right away, just as soon as the next one came, to call it a birdie.” The term eagle originated by analogy with birdie, being a score of two under par, and one stroke better than a birdie.