History of the word derives from a particular individual who wore brown pants to the office more than once. Even up to three times per week.
A pirate ship appears on the horizon. The captain says "Men, bring me my red shirt!" The first mate fetches the shirt and the captain successfully leads an attack on the pirates that sinks their ship.
One of the sailors asked the captain "Why do you wear a red shirt in battle?" The captain responded "because if I am wounded, you will not see blood and will continue to fight as if nothing is amiss." The crew was astounded at the bravery of the captain.
Later, twenty pirate ships appeared on the horizon. The men looked to the captain, waiting for the request that brought everyone so much strength. The captain looked at the horizon and said, "Men, bring me my brown pants!"