Although it's been around since 1473, the noun mural only started meaning "wall painting" in the early twentieth century. Before that, it could refer to fruit trees growing against walls, to the honors bestowed on the soldiers who were the first over an enemy's walls, or really anything to do with walls. The word comes from Latin muralis, which meant "of a wall" and was the genitive singular of murus, "wall". Muralis also gave us intramural, which translates to "within the wall" and was so named because it was applied to sports that took place within the walls of an institution (as opposed to extramural sports like varsity stuff). Murus is reconstructed as coming from the Proto-Italic root moiros, which in turn derives from Proto-Indo-European mey, a verb that could mean "fix" or "build fortifications".
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.