During the Middle Ages the city was called Arus, and in Icelandic chronicles, it was known as Áróss. It is a compound of the two words ār, genitive of ā ("river", Modern Danish å) and ōss ("mouth", obsolete in Modern Danish; in Modern Icelandic this word is still used for "river delta"). The name originates from the city's location around the mouth of the stream Aarhus Å (English: Aarhus River), Å being the Danish word for a small river.
Through regular sound development, Medieval Danish Arus became Aars or Oes, a form which persisted in the dialects of the surrounding parishes until the 20th century. In 1406, Aarhus became prevalent in the written sources, and gradually became the norm in the 17th century. Aarhus is probably a remodelling after the numerous Low German place names in -husen, possibly as a result of the influence of German merchants.