While you might think that noodles don't really look like heads, they do kinda look like brains. Originally “using your noodle” was an insult – comparing a simpleton wagging his head around while thinking with a wet, floppy noodle. Nowadays, it's no longer an insult and simply means "think about it."

What is noodle slang for?

1 : a stupid person : simpleton. 2 : head, noggin.

Where does the term noodle come from?

The verb “noodle,” meaning to fool around or waste time, has been in use since 1854, according to the Oxford English Dictionary. The OED says the word comes from the noun “noodle,” meaning “a stupid or silly person; a fool, an idiot,” a word that was first used in print in 1720.