The Polish traditional names for Venus as the Morning/Evening Star
are Gwiazda Poranna (or Zaranna) and Gwiazda Wieczorna (no "-iaia") --
descriptive terms like the English ones, and referring to the
celestial body, not to a deity (or deities). I'll check earlier names
(if any) in Old Polish, but "Dnieca" strikes me as implausible. I
suspect it is a phantom name quoted circularly by popular sources. I
don't think there are any records of a planet cult in Poland. At
these northerly latitudes the visibility of Mercury is very poor and
the early Slavs may well have been quite unaware of its existence
(though I don't believe in the apocryphal story of Copernicus
complaining on his deathbed that he'd never seen Mercury with his own
eyes; he would not have missed any opportunity to sight it during his
studies in Italy, if not in Poland).
Piotr
--- In cybalist@..., cas111jd@... wrote:
> The Russians have the goddess Vechernyaya Zvezda `The Evening
> Star', 'she of the aurora of Dusk/ Twilight', Pol. Wieczorniaia),
and
> the dawn-goddess Utrennyaya ('she of the aurora of Morning', Pol.
> Dnieca).