From Quinion World Wide Words

We use come a cropper now to mean that a person has been struck by
some serious misfortune, but it derives from hunting, where it originally
meant a heavy fall from a horse. Its first appearance was in 1858, in a late
and undistinguished work called Ask Mamma, by that well-known Victorian
writer on hunting, R S Surtees, who's perhaps best known for Jorrock's
Jaunts and Jollities.