The term "hub cap" comes from the days before cars. Wagon wheels had wood hubs that wood spokes attached to. Those hubs contained bearings that needed to be accessed to be greased. They were commonly called "hub caps" or grease cups, or dust covers, or grease caps. Later cars used spoked wheels with decorative caps that covered only the hub and grease cap. These are "hub caps". Lincolns in the 1940s used hub caps with trim rings.

Our cars have "wheel covers" that cover nearly the whole wheel. The wheel covers were designed not for our car, but for Cadillac. They look exactly like the wheel covers used on Harley Earl's personal car, the 1951 GM LeSabre concept car. They were proposed for a top-end Cadillac but were not used as they were too expensive, with 40 separate stainess-steel vanes.

Lyon Industries, located near GM Tech Center, is a large automotive supplier, but is more famous for making school lockers and steel kitchen cabinets, all the rage of the '50s.

I have found the best way to clean our wheel covers is in the dishwasher, two at a time.