Hi Mark,
I don't think it can be proven one way or another but it is more likely that the planets were named afterward (in Greek and Roman mythology anyway). Either way they are old.
Writing hasnt been around for that long, early religions were quite complex and even within the same religion gods were attributed differently from place to place and differently throughout time. The greeks called the planets 'wandering stars'.
If you go as far back in writing as possible (3000-3500BC) to the Sumerian/Babylonian religions the goddess Inanna was associated with the planet Venus (actually both the morning and evening star). Inanna was also the goddess of love and fertility (sounds familiar).I believe this was the case for the other planets and their major gods and may be due to their advanced knowledge of the planets.
http://en.wikipedia.org/wiki/Astrolatry
If you move back to the greek/roman the creation story and Jupiter (ie ZeusPater/ZeusFather/SkyFather) you mention Ioriginates from Hesiod (700bc) and actually Homer and Hesiod differ in their creation stories (however Hesiod's became more accepted) and when they mention the night sky they don't refer to the planets (i'm not sure doing so would have really worked for the context in the Iliad ... the gods were on mount olympos). And before anthropomorphism probably more naturalistic forces or deities, with Zeus/Jupiter being a sky god derived from the proto european
http://en.wikipedia.org/wiki/Dyeus
it would be interesting to know when the Greeks started to identify the wandering stars with the planets definitively - it may have been before Hesiod and Homer's time there's over a couple of thousand years for the Babylonian influence to spread.
More from the wiki
References to identifiable
stars and
constellations appear in the writings of
Homer and
Hesiod, the earliest surviving examples of Greek literature. In the
Iliad and the
Odyssey, Homer refers to the following celestial objects:
Hesiod, who wrote in the early 7th century BC, adds the star
Arcturus to this list in his poetic calendar
Works and Days. Though neither Homer nor Hesiod set out to write a scientific work, they hint at a rudimentary
cosmology of a
flat earth surrounded by an "
Ocean River."
http://en.wikipedia.org/wiki/Ancient_Greek_astronomy
Anyway i hope that helps and i haven't rambled too long:
... the earth, the heavens, and the sea; the moon also at her
full and the untiring sun, with all the signs that glorify the face
of heaven- the Pleiads, the Hyads, huge Orion, and the Bear, which
men also call the Wain and which turns round ever in one place, facing.
Orion, and alone never dips into the stream of Oceanus. Iliad