William Barlow "come[s] before you with one boot and one shoe." He arouses the wonder of the girls, is given free entrance to the races, and is more unusual than any animal in the circus. He hopes some young lady will accept him as a beau
Belden notes this as a comic song performed as far back as 1842, and popular enough to parody during the administration of Franklin Pierce (1853-1857). Belden also notes that Edgar Allen Poe refers to his ex-publisher as "Billy Barlow," implying that, by 1840, the name was already used for a buffoon.
Joy Hildebrand brings to my attention Sam Cowell (1820-1864), who performed as Billy Barlow. From the dates, it looks like Billy probably predates Cowell. But Hildebrand speculates that Cowell might have converted Billy into a character in the "Cutty Wren" type song "Billy Barlow (I)." So far, this is just speculation -- but it makes some sense. - RBW