Here's the bizarre reason people don't use the bottom button on suits

There’s a well documented rule when it comes to suits with three buttons, it’s as easy as: “sometimes, always, never” — Sometimes button up the top button, always button up the middle one, and never button-up the bottom one.

In a two-buttoned suit, one should always button up the top and never the second button.

But don’t take our word for it. Ask style mogul, Leo DiCaprio:

ALSO SEE: Kate Middleton channels Jackie O. during Easter Sunday service

But where did the tradition come from?

Legend goes that in the early 19th century, Britain’s King Edward VII grew too fat for his suit and had to stop using the second button as a result. Not wanting to embarrass him, everyone followed.

The “Edwardian theory,” as GQ U.K.’s fashion director Robert Johnson calls it, isn’t always taken seriously. It sounds too far fetched to be true. But historians of British fashion consider it fact — at least partly fact, the story has become a little muddled over the years.

According to Sir Hardy Amies, an English fashion designer who was the official dressmaker for Queen Elizabeth II for nearly four decades — suit jackets are unbuttoned at the bottom because they replaced horse-riding jackets.

In a 1992 lecture he gave to The Royal Society for the Encouragement of Arts, Manufactures and Commerce, Amies traced the story of “The Englishman’s Suit” from 1670 to his present day. The single-breasted suit of today was first introduced in 1906, at the time of Kind Edward’s reign, and was referred to as a “lounge suit.”

The lounge suit began to replace traditional riding coats. So they had to be unbuttoned so the jacket draped properly while someone was sitting on a horse.

Edward VII decided that the top button should also be undone because it “looked common,” according to Amies, leaving only the middle button done up.

It was however, the King’s growing belly that changed the style rules around wearing waistcoats.

“Edward VII always left his bottom waistcoat button open because he was fat,” said Amies. “He found it more comfortable and everybody copied it. Waistcoats are now cut for the last button not to be done up.”

ALSO SEE: A body language expert breaks down Prince Harry and Meghan Markle’s photos

The trend, the Oxford Dictionary notes, “was followed in this in Britain and the empire but not on the continent or in the U.S.A.” But nowadays, unbuttoning the bottom of the waistcoat is also the norm.

So there you have it. Let us carry on dressing (and eating) like kings!

Let us know what you think by tweeting @YahooStyleCA!