From Old Norse rass, metathesis of Proto-Germanic *arsaz, cognate to English arse, ass, German Arsch, Dutch aars, Norwegian rass, and Swedish arsle, arsel. Ultimately from Proto-Indo-European *h₃érsos.
rass m (genitive singular rass, nominative plural rassar)
- (ass): afturendi m (euphemistic), bakhluti m (euphemistic), bossi m (baby talk), sitjandi m (euphemistic)
From Old Norse rass, "behind, anus", akin to ars, from Proto-Germanic *arsaz, from Proto-Indo-European *h₃érsos; compare Icelandic rass, English arse, ass, German Arsch, Dutch aars and Swedish arsle, arsel.