Her name is Þrúðr („strength, power") and she is the daughter of Thor and Sif. Around her turns one of the craftiest poems of the Edda – the Alvíssmál.
The dwarf Alvíss („all-wise") appears and claims Þrúðr as his promised bride – the gods, he says, pledged her to him in Thor’s absence. Thor returns and is by no means content. Yet instead of reaching for the hammer he chooses a finer weapon: time.
Thor sets the dwarf a condition: he must prove that he is truly „all-wise" and name, for sun, moon, earth, sea, wind and more, the words in every world – among the Æsir, the Vanir, the giants, the dwarves. Alvíss, vain of his knowledge, answers verse after verse. He does not notice the night passing. As he finishes, morning breaks – and dwarves cannot bear sunlight. The first ray turns Alvíss to stone. Thor has saved his daughter with cunning, not with force.
“With great cunning, I tell you, you are beguiled: / above your head, dwarf, stands the day, the sun shines in the hall.”— after Alvíssmál 35, Karl Simrock (public domain)
The Alvíssmál is more than a cunning anecdote – it is a treasure-house of poetic language. In his answers Alvíss gives, for sun, moon, clouds, wind, sea, fire, ale and more, the names as they are called „among men", „among the Æsir", „among the Vanir", „among the giants", „among the dwarves" and „in Hel". So the poem preserves a whole dictionary of skaldic heiti (poetic synonyms) – a toolkit for every poet of the North.
And Þrúðr? Her name, „strength", also appears as a valkyrie-name (Grímnismál 36) and lives on in kennings for „woman". Whether Thor’s daughter, valkyrie or personification of strength – Þrúðr is a fine example of how fluid the borders are between goddess, warrior and concept in Norse thought.
Thor · The Dwarves · Valkyries · Mjöllnir.
Alvíssmál, Grímnismál (Poetic Edda); Snorri, Skáldskaparmál. Rudolf Simek, Dictionary of Northern Mythology.