squalid

This is one of those words that sounds dirty before you even know what it means. English picked it up in the 1590s from French squalide, which in turn came from Latin squalidus — a word for something rough, grimy, and literally coated with filth. The mystery is deliciously annoying: Latin itself seems to have borrowed the feeling of grime without leaving a neat family tree, so etymologists mostly stop and shrug. It stands beside cousins like sordid, which also stinks of moral and physical decay, but squalid has a more visual ugliness — the image of a room with stained walls, damp corners, and nobody coming back to clean it. If sordid is a dirty secret, squalid is the apartment you can smell from the hallway.