Cornish game hens: Despite the name, it is not a game bird, but actually a typical chicken that is slaughtered at a young age and therefore is smaller in size. Though the bird is called a "hen," it can be either male or female.
Most sources credit Alphonsine and Jacques Makowsky of Connecticut for developing the small bird in the mid-1950s. A Saturday Evening Post article from July 1955 credited Mrs. Makowsky with coming up with the idea to breed the Cornish game chicken, a small bird with short legs and a plump, round breast that she had discovered in a book.
I had never heard of them before.