When Peter had finished arranging the shapes he had cut out of heavy cardboard, his mother tapped the first one, and said, "Peterkin, this is called a triangle, from the Latin word triangulum, because it has three corners." Peter pointed to another shape and asked, "What’s that?" She replied, "It’s a pentagon. The Greeks called five pénte and the angled corners of shapes gōníā, so a pentagon has five pointed angles."