Cartouches are little boxes or ovals often surrounded by arabesque patterns which were used to provide additional information about a certain feature or to embellish features that are too small to see on a map or a diagram.
For example, on 16th century maps cartographers would put little icons of sea monsters and such pulling people of ships and devouring them. They also used cartouches to provide bits of historical info about the place. These would contain stuff like: "In 500 B.C. a caravan encountered a three-headed poodle in this mountain pass."
It's interesting how much more inter-related art and science used to be. You hardly see any of those cute pictures nowdays. Nonetheless, arabesque patters persist in software licenses and money.