King Edward VII had a large appetite and an even larger tummy.
He began leaving the bottom button of his vest undone because after a meal he simply couldn’t do it up.
Those who didn’t want to make the king uncomfortable did the same, and so it became the fashion of the day.
Edward’s bulging belly may in part have been a consequence of his favorite dish, which was, of course, chicken a la king.
And that’s how Edward VII made it fashionable to leave the bottom button of a man’s vest undone.