::I believe that's a case of false etymology.  Although di as a prefix can mean "two," not every word beginning with di has that meaning.  In this case, it's part of dion, a name associated with Zeus and perhaps other gods.  Even if that connection weren't so obvious, nothing in the rest of the name appears to be etymologically connected with "birth".  As attractive a theory as "twice-born" (or "borne") is, nysus has nothing to do with being born or carried.  It vaguely resembles the Latin word natus, meaning "born", but it would have to be Greek, not Latin, and it's too easy to be mislead by the fact that two words resemble each other.  Merely because one of them would produce a logical meaning if it were the one intended doesn't make it the correct etymology.