Nosferatu has been presented as an archaic Romanian word synonymous with "vampire". It was largely popularized in the late 19th and early 20th centuries by Western fiction such as the gothic novel Dracula (1897) and the German expressionist film Nosferatu (1922). One of the suggested etymologies of the term is that it is derived from the Romanian nesuferitul ('the offensive one' or 'the insufferable one').

One proposed etymology of nosferatu is that the term derives from the Greek nosophoros (Greek: νοσοφόρος), meaning "disease-bearing". The word appears to be quite rare in Greek. The variant νοσηφόρος ("nosēphoros"), is attested in fragments from a 2nd-century AD work by Marcellus Sidetes on medicine. Another variant appears in the Ionic dialect as νουσοφόρος ("nousophoros") in the Palatine Anthology.

Other etymologies connect the term to various Romanian terms. These include necurat ("unclean"), which is commonly associated with the occult, nesuferit ("unbearable, insufferable), and nefârtat ("enemy", lit. "unbrothered").

The word achieved currency through Bram Stoker's 1897 novel Dracula and its unauthorised first cinematic adaptation, Nosferatu (1922). Internal evidence in Dracula suggests that Stoker believed the term meant "not dead" in Romanian, and thus he may have intended the word undead to be its calque. He describes these creatures in the following passage:

For all that die from the preying of the Un-dead become themselves Un-dead, and prey on their kind. And so the circle goes on ever widening, like as the ripples from a stone thrown in the water. Friend Arthur, if you had met that kiss which you know of before poor Lucy die, or again, last night when you open your arms to her, you would in time, when you had died, have become nosferatu, as they call it in Eastern Europe, and would for all time make more of those Un-Deads that so have filled us with horror.

This seems to be the motivation for Leonard Wolf to gloss nosferatu as "not dead."

Stoker identified his source for the term as 19th-century British author and speaker Emily Gerard. It is commonly thought that Gerard introduced the word into print in an 1885 magazine article, "Transylvanian Superstitions", and in her travelogue The Land Beyond the Forest ("Transylvania" is Latin for "the land across/beyond the forest"). She merely refers to "Nosferatu" as the Romanian word for vampire:

More decidedly evil, however, is the vampire, or nosferatu, in whom every Roumenian peasant believes as firmly as he does in heaven or hell. There are two sorts of vampires—living and dead. The living vampire is in general the illegitimate offspring of two illegitimate persons, but even a flawless pedigree will not ensure anyone against the intrusion of a vampire into his family vault, since every person killed by a nosferatu becomes likewise a vampire after death, and will continue to suck the blood of other innocent people till the spirit has been exorcised, either by opening the grave of the person suspected and driving a stake through the corpse, or firing a pistol shot into the coffin. In very obstinate cases it is further recommended to cut off the head and replace it in the coffin with the mouth filled with garlic, or to extract the heart and burn it, strewing the ashes over the grave.