With profuse and profound thanks to Jen Steele and @SmithsonianMag:
The History and Psychology of Clowns Being Scary
This article - from Linda Rodriguez McRobbie - does a far more thorough and well-researched take on the origins of the scary clown archetype than I've ever managed. From Grimadli to Gacy, this is a concise yet thorough of the history of clown as provocateur.