The cubit is the distance from the bottom of the elbow to the tip of the middle finger.
This was an ancient Egyptian unit of measurement, along with the finger, foot, fist, and spam.
But surveyors had different body measurements, so measurement was a somewhat inaccurate science.
Standardization came when the pharaoh insisted that the measurements be based off of his body measurements.
However, it wasn’t easy getting time with the pharaoh to measure land or cloth.
And he tended to execute surveyors who dragged him around in the mud.
So, they found a similarly-built surveyor, and dragged him around.