Fun etymology fact: Both Frankfurts get their name from a simple description of the same thing, which they both are instances of: settlements adjacent to a Frankish river ford (place where the river is shallow enough to cross without a bridge). The English "ford" and German "Furt" come from the same root; hence Francoford / Franken-Furt / Frankfurt. The "an der Oder" (at the Oder) and "am Main" (at the Main) suffixes are clarifications to describe which river is involved.