What determines when a word is in currency as a trademark and when it has seeped out into wider usage? For example, a standard spellchecker will probably pull us up still if we typed "I hoovered the carpet", seeking to make it a capitalised noun. Yet I doubt if anyone thinks of it as only a brand name by now. Perhaps there is a period of parallel meanings, where the product has become so emblematic of the action that it is adopted to also denote the action, and (if at that point it is not somehow protected) it gains general currency...?

PS: The SC on this site wants me to make it Hooverise - I draw the line at that! It leaves me feeling quite disorientated.