In Scandinavian folklore, the mylingar were the phantasmal incarnations of the souls of children that had been forced to roam the earth until they could persuade someone (or otherwise cause enough of a ruckus to make their wishes known) to bury them properly.
The myling (also known as utburd in Norwegian, útburður in Icelandic and ihtiriekko, liekkiö or sikiö in Finnish) is said to chase lone wanderers at night and jump on their backs, demanding to be carried to the graveyard so they can rest in hallowed ground.
Mylings are thought to be enormous and apparently grow heavier as they near the graveyard, to the point where any person carrying one (or more) could sink into the soil.
The "extra-burden" meaning could also explain the motif or trope of the myling or utburd getting heavier as they're carried to hallowed ground to be buried.
The belief that mylings are enraged and seeking revenge is what gave them the reputation as one of the most menacing types of ghosts in Scandinavian folklore.