Dude underwear in the Middle Ages is something we actually know about. Commonly made out of linen (from the flax plant – but that’s material (*groan*) for another day), men wore versions of undershirts and boxers that tended to be loose and long (knee-length), but tied or tucked as the situation warranted. The undergarments were for warmth, but also to provide protection for more expensive outer clothing, which would not have been washed as frequently and were intended to last longer. Although fabric decays quickly, making physical remains hard to come by, historians get a great deal of information about men’s underwear from illuminated manuscripts, such as you see in the first image here. Although similar evidence exists for women’s undertunics, historians have no images for the ladies’ version of men’s boxers (called “braies”): to see the men’s gonad-coverings could have been considered humorous, but panties were evidently lewd. The second photo shows a Late-Medieval-style undertunic and braies from the company ArmStreet.
Source(s): See medievalists.net, “Overlooked and Undervalued: Underwear in the Middle Ages,” by Madeleine Colvin, June 2018. Image is from the Maciejowski Bible.