From Old Danish hurædan, where -dan is from Middle Low German wōdān, a compound of 1. wō (“how”) from Proto-Germanic *hwō, and 2. dān (“done”), past participle of dōn (“to do”), from Proto-Germanic *dōną. Compare Danish sådan (“so”), ligedan (“in the same way”)
In Medieval Scandinavian, the first part is remodelled after the adverb Old Danish hwaræ, huræ (a cognate of Swedish hur), from Old Norse hváru, a dative singular of hvárr (“which (of the two)”), from Proto-Germanic *hwaþeraz. In modern Danish, it is associated with the adverb hvor (“where”), from Old Norse hvar (“where”), from Proto-Germanic *hwar.
- “hvordan” in The Bokmål Dictionary.