Historically, the municipality was named Sør-Undal or Søndre Undal, which uses an older version of the valley name that had been corrupted and shortened over time as well as an alternate way of spelling "southern".
Historically, the municipality was known as Sør-Undal or Søndre Undal, embodying an older version of the valley name that has been modified and shortened through time, as well as a distinct spelling for "southern".