From A Brief History of the Vikings by Jonathan Clements, available in the UK and in the US.
There were a number of ungodlike enemies with which the Viking deities found themselves in conflict. A major group of rivals, for example, are the Jotnar, or Giants, a race whose names often contain elements of shifty duplicity, cunning, and braggadocio. If the Jotnar were a race supplanted by proto-Scandinavians, then we might even guess at their original home, Jotunheim, in south central Norway. The Jotnar are despicable to Norse eyes, violent and uncontrollable, creatures of the mountains, formidable foes, yet whose females are often regarded as desirable brides – a conqueror’s view of the conquered. A leading adversary of the Jotnar is Thor himself, whose legends contain many hints that associate him as an unwelcome guest in the Jotunheim region. His mother, for a start, is a giantess herself, Fjörgynn, a mistress of Odin. In an area where goat herding is a paramount local industry, we find that Thor quarrels with his neighbours over deaths of his flock. He rides in a chariot pulled by goats, and is sometimes referred to as Oku-thorr, the Charioteer – in both Old Norse and Sámi, the words for thunder and a wheeled vehicle are punningly similar.
In Lapland, some shamanic drums show a male figure bearing a hammer in one hand and a swastika (thunderbolt) in the other, said to be Horagalles, the Norse Thor-Karl, or ‘old man Thor’.One of the most famous stories of Thor tells of his fight with a giant who leaves a piece of stone permanently embedded in his head. This may be a reference to a ritual at sacred sites of Thor, involving the striking of flint. In other words, with his red hair and beard, and his mastery of lightning, Thor may have been a fire god, whose trials in myth are allegories of the kindling of sacred fires, and the smiting of foes.
Other races in the Viking mythos can be seen as similarly conquered peoples, associated in the Viking mind with a native mastery of the local woodlands and hills. Such peoples are the huldufólk, the ‘hidden folk’ identified in different parts of Scandinavia by different names, and ultimately combined by later writers to form a menagerie of supernatural creatures.The álfar or elves, for example, and their dark cousins the dvergar, or dwarves. Both are occasional allies of the gods, the dwarves renowned for their skills in metalwork, the elves as occasional bedmates and tormentors. At no point during the Viking age was there any implication of diminutive size in either of these races – their role as the ‘little people’ of later centuries is thought to have been a function of the suppression of old religions with the onset of Christianity.