* Cocked hats were a type of hat, typically worn by military officers, that had a distinctive, often pointed, shape that was curved upwards.
* French cocked hats were a particular style of cocked hat that was popular in France during the 18th century.
* Forehead is the part of your face above your eyebrows.
It's very unusual to wear a hat on your forehead. It's possible that the phrase is:
* A humorous description: Perhaps the person was wearing the hat in a silly way, perhaps tilted forward on their head, or even backwards on their head.
* A metaphorical expression: The hat could be a symbol of something else, like a person's arrogance or a sense of style that is considered old-fashioned.
* A misremembered phrase: The actual phrase might be something different entirely.
Without more context, it's impossible to say exactly what the phrase means. If you can provide more information about the situation or the speaker, it might be possible to understand the intended meaning.