The stemm-syllable has an au - o change as we see in Asbjörn - Osborn, Austrie etc., and this change in pronunciation happened sometime around 1400.

The English cognates of the original name would be "chapman's haven". The English chapman, German Kaufmann, Dutch koopman, Swedish köpman, Danish købmand, and Icelandic kaupmaður share a derivation from Latin caupo,