What about the other planets visible to the naked eye?How did medieval Europeans refer to our most familiar astronomical objects?
Yes, it was called Jupiter in Roman times (or alternatively the 'star of Jupiter').
The Roman names are translations from Greek names, which are in turn adaptations from Babylonian practice. So for example 'Jupiter' came from 'star of Zeus', which in turn came from 'star of Marduk'. Babylonian astronomy effectively gave the planets two names: (1) an actual name, and (2) an association with a god. It's the divine names that got borrowed.
The equivalences between pantheons aren't consistent, and there was some variation: for example in Greek, Venus could be called either 'the star of Aphrodite' or 'the star of Hera', both corresponding to Ishtar in the Babylonian naming system. In Latin, the name 'Venus' became standardised.
I gave a fuller answer on this a couple of years ago -- but I'm quite certain there's still more to add.