About the Riordan surname
For the surname Riordan, no single etymology is selected without a sufficiently specific source. The canonical form used here is “Riordan”; phonetic or spelling differences found in indexes should be checked against the other information in the record. The earliest records help place the name in its geographic and family context before drawing conclusions about its origin.
Pronunciation:
Rior-dan/ʁiɔʁdɑ̃/