Near the end of the Western Han dynasty (206-23 B.C.) there was an ambitious young man named Ma Yuan who was well-educated, adept at the martial arts, and dearly beloved of his older brother. When his brother died, Ma Yuan took care of the funeral and respectfully looked after his sister-in-law.
Later, he was made a local police official and charged with escorting a prisoner to another location. Along the way he saw that the prisoner was weeping bitterly. Moved with compassion, he let the prisoner go and ran off to the North.
In the North, Ma Yuan raised several thousand sheep and goats for a living. "A real man gets tougher in poverty and stronger with age," he told himself. All the money he made he gave to his friends and relatives, living very frugally himself.
Later, during the Eastern Han dynasty (25-220 A.D.) Ma Yuan become a famous and successful general. People used the expression "stronger with age" to describe a person advanced in years but still hale and hearty.