A Gjenganger (Norwegian: Gjenganger/Gjenferd/Attergangar Danish: Genganger/Genfærd Swedish: Gengångare) is the term for a revenant, the spirit or ghost of a deceased from the grave, in Scandinavian folklore. Gjenganger has two parts, the prefix is related to "again" or "against", "towards" (gegenüber, gegen) and í gegn ('against'), from í ('in, on') and gegn ('straight, direct') and ganger which comes from a word meaning 'foot' or 'walker', thus it means "walking again" as in "walking after death". The form "attergangar" comes from atter meaning 'after' and originating from *afteraz meaning "of, away from" but adding the contrastive suffix *-teros, in essence meaning "after walking", "walking away from in contrast with close by", again imlying walking after death.
A gjenganger could have several reasons to return from the afterlife. Murdered people could seldom sleep peacefully in their graves. The same went for their murderers. People who had committed suicide often came back as gjengangere, because Christian tradition held that "self-killers" were fit neither for heaven nor hell. At other times, people came back from the grave because they had left something undone. Most often they needed someone to help them do this, before they could finally be at peace.
The biggest difference between modern ghosts and the gjenganger is that the gjenganger in the Scandinavian tradition took on an entirely corporeal form. It normally had no spectre-like qualities whatsoever. In older traditions the gjenganger was also very malicious and violent in nature, coming back from the grave to torment its family and friends. In the way they acted, and in the extensive precautions their relatives took to make sure they stayed in their graves, gjengangere are more akin to eastern-European vampires than modern-day ghosts.
This tradition of the violent gjenganger goes back to the Viking age, where they are present in many of the Icelandic sagas, among others: Grettis saga, Eyrbyggja saga and The Saga of Eric the Red. In this tradition, the gjenganger was a mortal creature. An example of this is Grettir slaying the gjenganger Glámr with his sword. These Viking-age gjengangere were often called draugr, and the two are likely to be different names for the same phenomenon.
In slightly newer tradition, the gjenganger remains a violent entity, though in a less direct way, now becoming more of a disease-spreader. These gjengangere would attack people with their so-called dødningeknip (dead man's pinch). This would result in the living persons skin becoming sunken and blue where the gjenganger had pinched them, and this often led to disease and death for the afflicted person. The pinch was often administered when the person was asleep. Both the huldrefolk and nøkken were also accused of doing the same, using bites instead of pinches, often aimed at the victims face. This belief in beings attacking people in their sleep was used as a warning against going to sleep in specific places (near the graveyard, mountains or water respectively).
In later Swedish folklore, a distinction is made between the traditional gjenganger, in Swedish called gengångare, and another type of ghost known as gast. Whereas the gengångare looked virtually identical to a living human, the gast was known to be transparent and/or skeletal in appearance, sometimes it also had sharp fangs and claws, thus making it impossible to see who the phantom had been while alive. And whereas the Swedish version of the gengångare (unlike its counterparts in other Scandinavian countries) were usually said to be rather harmless, it was the gast who was known to cause diseases. They were also known to cause accidents and scare people for no apparent reason other than that they enjoyed doing so.
People had numerous ways of both defending themselves against the gjenganger, and stopping people from becoming one in the first place. A few of them are mentioned here:Crucifixes and Christian incantations to ward off the gjenganger.
Painting symbols, especially the cross, with tar above your door was said to ward off all kinds of supernatural powers.
When a person was buried, the coffin was carried over the church wall instead of through the gate (to stop him from coming back)
For the same reason, the coffin was carried three times around the church before being buried.
The shovels used to dig the grave were left behind, often on the grave itself in the shape of a cross.
If the coffin was carried to church on a sleigh or other wooden transport, the transport should be left behind to rot, or be used by poor people as firewood.
Perhaps the oldest example we have of an attempt to stop someone from coming back as a gjenganger, is a runic inscription from the 6th century. It was written on the inside of the grave, facing the dead and reads:
For Birginga riste broren runer
Kjære syster mi, skån meg!
For Birginga, the brother carved runes
My dear sister, spare me!
A tradition that deserves special mention is that of the "varp". A varp is a pile of stones or twigs which often marks a place where someone has died. It was believed that when you passed this place, you should throw another stone/twig on the varp, to commemorate what had happened there. Doing so would sometimes bring luck on your further travels, while not doing so would result in bad luck and dangerous accidents. Many of these varps have now disappeared, especially the ones made out of twigs. But in a few places the varp is marked with a sign or something similar, and the tradition is kept alive to this day, though in a much looser, and often joking, manner.
Ever since spiritualism came to Scandinavia around the beginning of the 20th century, the perception of the gjenganger has been gradually altered. Today it mostly compares with the modern perception of ghosts, most often being ethereal in form, and non-violent in nature. The word gjenganger is seemingly being used less and less, the contemporary word spøkelse (ghost) having mostly taken over.