Answer: Moustache

If you look closely at the royal cards in a deck of playing cards, you’ll notice one tiny little detail: all the kings, save for the King of Hearts, have moustaches. While we’d love to regale you with a fanciful story of why the King of Hearts lacks hair on his upper lip, the rather mundane reason is piracy (and not the high seas kind).

The Kings, Queens, and other royal cards were given actual images (instead of just symbols) by French card makers in the 16th century. Mass production via wood-block printing led to distortions in the image (as the blocks wore down and weren’t tended to properly by harried operators) and the King of Heart’s moustache became less distinct. When English card makers stole the designs of the French card makers, the moustache vanished altogether as the samples the English were copying were the later sets where the King of Hearts had no moustache.

Another shift in design, less explainable by the woodblock wear and design piracy, is that the King of Hearts lost his ax. In the original designs, the King of Hearts and the King of Diamonds both had axes, and the King of Spades and the King of Clubs had swords. Somewhere in the transition between the French designs and the English designs, the King of Hearts adopted a sword and left the King of Diamonds as the sole axemen on the throne.