Addan in the Bible Encyclopedia - ISBE
ad'-an ('addan; in Neh 'addon; connected in some way with the
name of the god Addu): A name mentioned in the list of the
returning exiles (Ezr 2:59, duplicated in Neh 7:61). It is one
of several names of Babylonian localities from which came men
who were unable to declare their genealogy as Israelites.