A suddenly idea occurred to me:
Bernal proposes Poseidaon < *P- Sidon, which
doesn't convince me.
My idea:
POSEIDAON < *NEPOSEIDAON < *NEPOT-SEIDAON,
changed by association with POTIS.
I mean: the "mix" of IE *Nepot with an obscure
*Sidaon or Tsidaon.
Joao SLRio