A “proprietary eponym” is a word that began as a brand name, but has come to mean the generic product (also called a “generic trademark,” apparently.)

Some of these are obvious and well-known, like rollerblade for in-line skate, kleenex for tissue, and xerox for photocopier, but I didn’t know until just know that heroin is also a proprietary eponym.

I’m also not sure just how embarrassed we should be that we need a word or phrase for this. At least a little, I would think.