Look in the margins of medieval books and you’ll find an unusual theme: knights vs. snails. Vox’s Phil Edwards investigates why in this episode of Vox Almanac.

Scholar Lilian Randall provides the best theory for the unusual motif: these medieval knights fought snails in the margins because snails represented the Lombards, who had become widely despised lenders throughout Europe. Snail was an insult and, over time, it became a type of meme detached from its original meaning.

Like much of art history, this theory is just a theory. But it gives us an insight into the rich culture of marginal art and all the complexity, confusion, and amusement that sits on the side of the page. You can read Randall’s paper here.