Sitzfleisch

Sitzfleisch: a term used in chess to indicate winning by use of the glutei muscles--the habit of remaining stolid in one's seat hour by hour, making moves that are sound but uninspired, until one's opponent blunders through boredom.

Just as he was snorting and puffing like a grampus, I chanced to observe a quite formidable scar on his Sitzfleisch. With an apology for the personal nature of the question, I asked if it was a war wound of some kind.