My record of Old Norse and Icelandic terms and Eddic references I encounter in reading.
Dísir
The dísir (singular: dís) are a complex spiritual concept in Norse mythology. They're female, they may be the spirits of dead female ancestors, and they take on dual roles, mortal and divine, without clear distinction. One of their aspects is that of a tutelary or guardian spirit over a family unit or clan, not unlike the Greek genius. The Norns, spinners of fate and nurturers of Yggdrasil's roots, and the valkyrja, Oðinn's battle-maidens who retrieved valorous souls who died in combat to bring to Valhalla, were all consistently referred to as dísir. The three Norns dictated the course of fate, working by rules unimaginable to us, indifferent to our plight; the valkyrja were not only undertakers but also lovers to heroes and sometimes rebellious and willful against Oðinn. Þorgerðr Hölgabrúðr, referenced in Njáls saga and Harðar saga among others, is a dísir as she represents the goddess of her land, a giantess, and the bride to the ancestral rulers of Hålogaland—all at once.
References: Norse Mythology for Smart People; Vikingr
Draug (Norse), draugr (Icelandic)
A type of demon known to sail in the back alf of a small boat, a draugboat. When the draugr is dressed as a person, it typically hides its face in a large hat. One reportedly wore a quantity of seaweed in place of its head. It can transform into a large seal. By one report, anything thrown at the draug does no harm, but the object is redirected at the thrower with at least as much force. In another story, a sailor stabbed a draug with a gaffe. The iron hook remained lodged in its back. It haunted its assailant, creating the illusion of a boat and challenging him to a race. It then conjured a storm and turned itself into a crew of corpses.
Galdr, gandr
Galdr is magic ("spell"); gandr is black magic. One who practices gandr has gan- as a prefix to their name.
Galdrakver
A book of everyday spells and candrips.
Gubber, goldgubber
Tiny plates of gold (7–20 x 3–12 mm) stamped or cut out. One type features a clothed man and woman in an embrace; most only feature a man, a few feature a boar. The puruity of gold is high, though some "cheated" with gold/silver and gold/copper alloys. That they were hammered so thin suggests they weren't exchanged as currency, despite the quality of the gold. Instead, it's believed they were used exclusively for religious offerings. They are usually found in high-status buildings as offerings to the Vanir, rarely in graves.
Reference: John McKinnell, Meeting the Other in Norse Myth and Legend (2005)
Lindworm
A large (10 m), pale, legless dragon or serpent that inhabits the cellars of abandoned churches.
Seiðr
(pron. SAY-der; from "cord, to bind") A form of pre-Christian Norse magic and shamanism. There were rituals for divination and clairvoyance, summoning that which was desired, or curses. As seiðr dealt with fate, the Norns were the masters of this magic. The practitioner of seiðr is called a völva.
Völva, vǫlva
(pron. VOL-va; from "staff bearer" or "wand carrier") Practitioner of seiðr, always female; also called prophetess, soothsayer, or witch. She could be a spiritual leader or healer. Men who practiced magic, seiðrmann, were seen as unmanly; a man could be castrated to learn magic, to a limited extent, as in the cult of Skaði. The Christian church hated/feared the völva and banned the use of staves and wands and heathen altars. It is recorded that some Jötunn learned seiðr, though it's unclear how. At one point, Oðinn summoned a völva from the dead for advice. Heiðr ("bright, honor") was a famous völva, described as a joy to evil women (read: women that men couldn't control).