What is the latin root word for loony?

There is no direct Latin root for "loony." The word "loony" is a slang term, likely derived from the word "lunatic," which itself comes from the Latin word "luna" meaning "moon."

The association between the moon and madness has been around for centuries, with some believing that lunar phases influenced mental instability. This association is reflected in words like "lunatic," "lunacy," and "lunar."

Therefore, while "loony" doesn't have a direct Latin root, it's ultimately connected to the Latin word "luna" through its history and meaning.