The Gothic form of the prefix was auda- (as in e.g. Audaþius), the Anglo-Saxon form was ead- (as in e.g. Eadmund), the Old Norse form was auð-.
The given name Otis arose from an English surname, which was in turn derived from Ode, a variant form of Odo, Otto.
Due to Otto von Bismarck, the given name Otto was strongly associated with the German Empire in the later 19th century. It was comparatively frequently given in the United States (presumably in German American families) during the 1880s to 1890s, remaining in the top 100 most popular masculine given names in the US throughout 1880–1898, but its popularity decreased significantly after 1900 with increasing anti-German sentiment leading up to World War I; it fell below rank 200 in 1919, below rank 500 in 1947, and below rank 1000 in 1975; it re-entered the top-1000 most popular given names in the US only in the 2010s, ranking 696th as of 2013.
^Förstemann, Altdeutsches Namenbuch (1856), s.v. "Aud" (161–180). Förstemann calls the element "excessively frequent" (Ein unendlich häufiger wortstamm). Spelling variants listed for the short form are: Audo, Auto, Oudo, Outo, Outho, Aoto, Aotto, Oato, Odo, Odda, Oddo, Oto, Otto (8th century), Otho, Ottho, Odto, Hodo, Hoto, Hotto, Hottho, Ootto, Ocdo, Octto. The surviving signatures of the Ottonian kings mostly read Otto, sometimes Odo or Oto. Listed as variants surviving into Modern High German are: Hoth, Hotho, Oette, Ott, Otte, Otto, Otho. The similarity of the Roman cognomen Otho is entirely coincidential. The spelling Otto is first recorded s.a. 744 in the charters of the Diocese of Constance (ed. Neugart, codex diplomaticus Alamanniae, 1791) and becomes increasingly common in the high medieval period.