Did you know Thermos was once a trademark? How TM ceases to be trademark and thus loses protection.

Trademark is a name, character or symbol that identifies the seller’s products and services. It happens, so, that trademark ceases to be just trademark, but becomes a common noun. This happens when product entered the market for the first time and does not have the specific name, the product had no competitors before, or there is no simple word in language for designating such item.
For owner, trademark becoming common noun carries the certain danger – trademark loses its legal protection and other producers can use its name. And even when the product leaves the market, it is so rooted in the minds of consumers they continue to call by its name products of other brands. It happened with TM Thermos. Today – this is the specific name and once was TM. Almost the same thing could be with Xerox.
There are companies trying to fight establishment of the trademark as the common noun. At the time, Xerox eradicated the word “xerox” from English and introduced “photocopier”, “photocopy” instead. Carrying out special advertising companies in countries of former USSR, Xerox company could not eradicate word from common use of consumers.