If I were to flip you the bird left-handed, which I sometimes do to mix things up, you’d notice that my middle finger is crooked, with a bulged knuckle. Why does it look like that? Catfish noodling.

Julia Kagan is a financial/consumer journalist and former senior editor, personal finance, of Investopedia. Suzanne is a content marketer, writer, and fact-checker. She holds a Bachelor of Science in ...