I have a pet-name for my wife and she for me. It's very common, but here's a funny one that you wouldn't expect belongs to the Queen!
This from Best Life- According to royal insiders, even Prince Philip has a secret nickname for Queen Elizabeth. It’s not your typical sweetie or honey. Apparently, Philip calls his wife of 72 years … cabbage. Yep, like the vegetable. It apparently comes from the French endearment, “mon petit chou”[mon pet-ee shoe]-- which is a way of saying “my darling.” However, the English translation is “my little cabbage.” (Best Life)