"John Brown's Body" (originally known as "John Brown's Song") is a marching song about the abolitionist John Brown. The song was popular in the Union during the Civil War. "Say, Brothers, Will You Meet Us", the tune that eventually became associated with "John Brown's Body" and the "Battle Hymn of the Republic", was formed in the American camp meeting circuit of the late 1700s and early 1800s. According to an 1890 account, the original John Brown lyrics were a collective effort by a group of Union soldiers who were referring both to the famous John Brown and also, humorously, to a Sergeant John Brown of their own battalion.
The most famous variant version is Julia Ward Howe's "The Battle Hymn of the Republic," which was written when a friend suggested, "Why do you not write some good words for that stirring tune?"