By similarity of attributes. The Greeks don't seem to have believed
that their gods might not be venerated in another country. To them,
the question would not be, 'Do you have an equivalnet of Hermes?': it
would ne, 'Who is the equivalent of Hermes.'.
> And the root Her- has the root for fire/heat that shows up
> in various forms across various language families e.g. even Turkic
> kIz (to heat up, get angry) < *kIr, Chuvash xer.
It would be a very unusual h- in Greek that has anything to do with a
velar consonant. The normal origin for h- in Greek is PIE *s-. The
only other origins are as a prothesis to u- and, occasionally, from