R.I.P. Zipper
Coined 1923 · generic for the fastener, but never for the boots
The story
B.F. Goodrich coined 'Zipper' in 1923 for rubber BOOTS fitted with Gideon Sundbäck's new slide fastener. Sundbäck had patented the mechanism, not the name. The catchy word slid off the boots and onto the fastener itself, where it became the ordinary name for the thing. Goodrich's exclusivity ended up confined to its boots; nobody could stop the rest of the world calling the fastener a zipper. Notably, no court battle was needed: the public simply decided.
The moral
Your brand may wander off and marry a different product entirely.
One grave, one class of goods. Genericide is decided jurisdiction by jurisdiction and class by class, which is exactly why the same word could die for fasteners and live for footwear. Zipper is the cleanest illustration in this graveyard.