With Samhain approaching I decided to write about the Dearg Due, the closest to a classic vampire that can be found in Irish folklore. Almost immediately though I ran into a slight problem, in that I can't find any references to this being in actual books on folklore. The only sources in which I could find the Dearg Due mentioned were more modern works and mostly ones that focused on vampires specifically. This has left me a bit skeptical of the Dearg Due's true origins, but nonetheless I'll relate the story here. It is the time of year for ghost stories after all.
First a bit about the name. Many sources will explain this name as meaning 'red blood sucker' but I think this unlikely. Dearg does indeed mean red, but Due is a more difficult word to interpret. In Old Irish the name may mean 'red owing' or 'red place', but I think it's more likely the name comes from modern Irish 'Dearg Dú'* which could be read as 'red evil' or 'red darkness'. As far as I can tell the words blood and sucker aren't involved.
So, the story then. As it goes around the internet and in the vampire books: Long ago in Ireland there lived a beautiful maiden, the daughter of a rich and greedy father. Many men came from across the land to try to win her hand in marriage but the girl had fallen in love with a local peasant and refused all others. Her father wouldn't allow this and forced her into a loveless marriage with an older man who was terribly cruel to her. Eventually, when she realized her true love wasn't going to rescue her, the girl killed herself. Before dying the girl renounced all that was good in the world, cursed God and those who had made her suffer in life, and swore she would get her revenge. And so it was that after she was buried she rose again from her grave as the Dearg Due; some say that she hunts and kills those who are guilty of hurting others, while others say she seeks out the innocent, especially children and young men to be her victims.
Like traditional Western European vampires the Dearg Due is a human being who died and was buried, and rose from the dead to torment the living. Like those other vampires she roams the night seeking to steal the life force from the living. Unlike other vampires the Dearg Due is not a type of being but a specific individual, and it is said her grave still exists in county Waterford. She only rises from her grave once a year on the anniversary of her death and she can be held in check if stones are kept piled on her grave.
It's hard to pin down how old these stories are or whether they are truly rooted in older mythology or represent a blending of newer thoughts. Certainly they lack the overt fairy folklore we see in the stories of beings like the Baobhan Sithe of Scotland which are also vampiric in nature, or even the more bloodsucking types of Leannán Sidhe found across Celtic speaking countries. But the stories of the Dearg Due are interesting and at the least represent an evolution in folklore as different cultural influences came into play.
*dú in this case is a form of dubh, literally meaning black