R.I.P. Escalator
US registration 1900 · generic in the United States since 1950
The story
Charles Seeberger registered ESCALATOR in 1900 for his moving staircase, and the rights passed to the Otis Elevator Company, which built the business. Otis then did the one thing you must never do: it used "escalator" as an ordinary noun in its own patents and its own advertising. When a rival, Haughton Elevator, petitioned to cancel the registration, the Commissioner of Patents agreed with the public and with Otis's own copywriters - an escalator is just… an escalator. Haughton Elevator Co. v. Seeberger, 85 USPQ 80 (Comm'r Pat. 1950).
The moral
If even YOU use your brand as a noun, the trademark office will too.
One grave, one country. Genericide is decided jurisdiction by jurisdiction and class by class: the same word can be the generic name of a product in one country and a live registered mark for the same goods in another. What is described here is the United States.