>Odysseus - Ulysses
>Whence did these opposing names for a single character emerge? Was the
>latter an Etruscan change of some sort?
The relationship is unclear. There are forms with -l- already in Greek (see
Sihler "New Comparative Greek and Latin Grammar" section 151), but it could
also be part of the sound change d > l in some Latin words, which is
possibly simply dialect borrowing.