We could adopt the Greek spelling: Eridanos, with the accept on the last syllable.
A number of rivers have the -dan- element in them, besides Eridanos: Danube (Danuvius), Rhodanus (the Rhone). River names are often taken over by new populations so these could go back to a very early time.
The Jordan River (Iordanes in Greek) looks similar but may not belong with the other examples (Hebrew yarden).