In ancient Assyria, the evil ghost of one who was denied entrance to the underworld and was doomed to wander the earth. Ekimmu means "that which is snatched away." One became an ekimmu by dying a violent or unsavory death, such as being murdered, in battle, drowning, or succumbing to exposure in the desert, which left the corpse unburied. The spirits of buried corpses also could become and ekimmu under other conditions: if the proper funeral rites were not observed at graveside; if the person died without surviving family; or if the spirit had no one to care for it.
The ekimmu was greatly feared, for it would attach itself quite easily to virtually any living person regardless of whether that person had been acquainted with the dead one. So much as looking at an impure corpse could result in being haunted by the ekimmu. At the least, the ekimmu was a nuisance, and at the worst, it could cause the deaths of an entire household. Once attached to the living, it was extremely difficult to exorcise.
The ekimmu also appeared as a death omen outside of houses, wailing in the same manner as the Irish banshee.
(Encyclopedia of Ghosts & Spirits: Ellen Rosemary Guiley)