Heads up, Meghan Markle!

Life in Buckingham Palace comes with a whole host of seemingly arcane rules. And nobody takes those rules more seriously than 92-year-old Queen Elizabeth, who might as well be the last of the Old Guard.

When the beloved British monarch is around, there are restrictions on what you can wear, what you can eat, and even what time you can go to bed. And now, thanks to an old Us Weekly piece that recently resurfaced via CheatSheet, we know that there are even limits to what you can say around her majesty. It turns out that the word she finds most vulgar, might be of particular interest to Meghan Markle at the moment.

WATCH: Queen Elizabeth Reacts to Meghan Markle and Prince Harry's Baby News

A palace source reportedly told Us Weekly that the Queen finds the word "pregnant" to be a "vulgar" word. Instead, the Queen prefers to say that pregnant women are "in the family way" as a politer, albeit old-fashioned, term.

Whatever floats your boat, your majesty!