As knights came to wear increasingly heavy metal armor in the thirteenth and fourteenth centuries, they needed some form of comfortable undergarment to provide padding for their body. The pourpoint was that garment. Heavily quilted and padded in key places where sharp parts of the armor contacted the skin, the pour-point was a close-fitting, long-sleeved shirt that buttoned down the front. It had carefully tailored arm sockets to allow complete range of movement for the arms which was key in battle.
The pourpoint was designed to make the wearer comfortable beneath his armor, but it was when the knight took off his armor that the pourpoint made a fashion statement. Like several other forms of medieval clothing, the pourpoint was tailored close to the torso. The hose that knights wore on their legs had ties that secured directly to anchors on the pourpoint, called points. The unarmed knight in snug-fitting hose and pourpoint became one of the first images of strength and masculinity to influence fashion, for this image was widely copied in paintings and tapestries of the day.
Payne, Blanche, Geitel Winakor, and Jane Farrell-Beck. The History of Costume. 2nd ed. New York: HarperCollins, 1992.