Do you know the English system for measuring foot length goes back longer than you would imagine? It was introduced in 1324 at the behest of King Edward II.

He decreed that three barleycorns laid end to end was the equivalent of an inch. 36 barleycorns end to end were the length of a man’s foot and as each barleycorn was a third of an inch it added up to 12 inches or one foot.

The longest foot at that time measured 39 barleycorns or 13 inches and so it was deemed to be size 13.

Smaller sizes were graded down by a third of an inch. Eventually, the sizing was deemed too crude a measure to be accurate and so half sizes were introduced.

The current measuring system is based on this.