How did “show the white feather” originate?

To show the white feather, which means to prove cowardly, retreat or back down, is a product of the cockpit. It was suggested by the old belief that a white feather in the tail of a gamecock was a sign that the fowl was crossbred and a mongrel, and consequently lacking in courage, pluck and fighting qualities. We have a similar idea in cur, which is applied to a mongrel dog supposedly inferior because of crossbreeding. It is said by cock fighters that when a purebred bird is pitted in combat against a mongrel bird the mongrel cannot stand the gaff and soon shows the white feather: that is, reveals its inferior blood by not being game. A [437] gaff is a metal spur attached to the leg of a. gamecock. A few years ago the United States Department of Agriculture commented on this subject as follows: “While it seems logical that selective breeding for courage and fighting qualities should result in the production of individual birds or strains best suited to this purpose, it is rather difficult to understand why the phrase to show the white feather refers to birds of mongrel breeding. In the old English game birds, color and markings were not of great importance, but a hard plumage was desired.” The original idea expressed by the saying may refer to the fact that a pure-blooded gamecock with white feathers in the wings would “show the white feathers” when he drooped his “wings and acknowledged defeat,