The term "Nosferatu" came from the piece Transylvania Superstitions, a book by nineteenth-century author/speaker Emily Gerard. Bram Stoker actually credited his using of the word from her book. Although Stoker suggests in his book that the word translates from Romanian to "not dead," Gerard claims that it is the Romanian word for "vampire." When commonly used in the western world, the word is associated with illness and disease. This may be rightly so, since the etymology of Greek shows the word "nosophoros" means "disease-bearing." From Stoker's famous book on throughout the history of vampires to the current day, vampires have commonly been portrayed as holding some sort of disease, or sickness.
Although the exact tracings of the whereabouts for the term used in this movie are uncertain, there are a majority of historians/linguists/etymologists that feel that these origins seem more than likely to be true. It is interesting to see how certain words have been used throughout the time of the talking man, and it is likewise interesting to see how words are commonly used in many different countries, being spread around and widely-used in books and the modern cinema.