Wellies for rubber boots sprang to mind.
Then I got thinking about kleenex being the word for tissue for most people where I live.
Some time ago xerox was a photocopy but that one has gone away.
Language does interesting things regionally...
Sounds like the German inventor called his version of acrylic plastic Plexiglas and it was one of the first to the market. Also seems like it is a trade name in some jurisdictions today.
So you google it and you get things like "is all plexiglas Plexiglas?" with answers like... it depends.