There was once an emperor in China named 'King Zhou' who was the last king of the Shang Dynasty. He was one of the most heartless tyrants ever to rule the empire, along with his wife Daji, who committed atrocities so evil she was thought to be a wicked fox demon in disguise.
One day, according to legend, King Zhou and Daji were sitting together on a riverbank drinking wine when they spotted an old man and a child, crossing the river. It was relatively shallow, and the child was able to swim across quickly. However, the old man lagged behind slightly, struggling to keep up.
Seeing this, Daji asked her husband to explain it, and asked whether it was their bones or their muscles which caused the main difference. King Zhou replied that it was their bones, because a child's bones were more dense and therefore affected less by the cold temperature of the water, however an old person's bones were less dense, almost empty, therefore the cold would feel more painful. Daji disagreed, saying that it was muscle weakness which drained the old man's strength. She argued that she had never heard of such a theory before.
Just to prove his point, King Zhou ordered two men to drag the child and the old man onto the riverbank. Then, they were ordered to cut open their shins with an axe and sample the bone marrow inside.
He showed Daji what he meant and she laughed, saying she knew it from the beginning, and she was only testing him. Then, they both left and went back to the palace.
From that day on, the citizens of China referred to that river as the 'Broken Shin River' (折胫河) and it is recommended that all who go near the area where the river was should beware of bad luck.