The genericizing of a proper name, brand name, or trademark into a common term to the point that the namebrand is thougt of as the *product* not as the 'name'.
(yes i realize many of these are somewhat regional/us-based but i am sure this phenomenon exists elsewhere as well. add them, or /msg me for additions)

for example:
-xerox = photocopy
-coke = any soda (limited, somewhat, to the south regions of the U.S.)
-sharpie = permanent marker
-kleenex = nose tissue
-scotch tape = clear tape for wrapping packages, hanging things, etc.
-saran wrap = clingy clear cellophane wrap
-hoover = vaccum cleaner
-dustbuster = handheld vaccum thingamajigger

it has been mentioned that copyright misnomer is in fact "a misnomer itself" as these are *trademark* issues and not copyright ones. However, as "copyright misnomer" is the phrase i have heard used to describe this phenomenon it is what i chose to node it under.