If you want to say that you have a crush on someone, you can say “J’ai le béguin pour toi” (zjay luh bay-gahn poor twah). This slang term has really old roots that date back to the Middles Ages. Béguines were women who withdrew from the world in communities like nunneries in the area that is now Belgium. The women wore distinctive bonnets that were known as béguins. How the meaning leapt from a bonnet to having a crush is rather mysterious.
Cole Porter composed “Begin the Beguine” in 1935. Here, the word beguine refers to a close, slow dance. The lyrics croon:
So don`t let them begin the beguine
Let the love that was once a fire remain an ember
Let it sleep like the dead desire I only remember
When they begin the beguine
The song became enormously popular and was recorded over and over in the following decades, including by smooth-voiced Ella Fitzgerald, above. So a bonnet became a dance and then became a way of expressing affection. The development of language is an amazing thing.