Persephone was a bride held against her will because she was tricked into eating food of/from/in the underworld by its king; in the film, she is a disillusioned bride, and you can see what kind of food the underworld’s king serves, and draw your own pomegranate parallels and imagine their backstory. Bonus points if you notice the modem noises when she kisses Neo – more fruits of trickery? In the movie, the Merovingian claims to rule over an exiled kingdom of programs whose lineage can be traced to the original Matrix. Historically, the Merovingians were a race of Franks who claimed divine lineage from Christ but were supplanted and all but wiped out when Charlemagne came to power. (I feel that these two characters, new in the second movie, had a much larger role in Neo’s choice than was obvious on a first viewing)
Neo means “New” and is also an anagram of “One” – take what you want away from that, since it is a perfect hero/savior/prophecy-figure name. Morpheus was the king of dreams, and in the movie, is soundly criticized as a dreamer; he is also, however, one of the best warriors in the realm of dreams (that is, within the Matrix, he is something of a God among men). Trinity means a gathering of three; whether this makes her the “third” member of the team, or whether it’s meant as a hint that Morpheus, Neo, and she are respectively a father-figure, a Messiah, and a guiding spirit.
Smith is both a generic name meant to convey the idea that an Agent “could be any- or everyone”, and a name that means “maker” or “builder”. However, the origin of the name comes from the same root as “smite” (because the first smiths made their craft by smiting or striking hot metal into useful tools). The allusion to violent creation and re-making is appropriate.
The names that the Zionists give to things like their home and their ships are all taken from ancient times. Nebuchadnezzar means “may Nabu protect the border”; he was a general and a king, and this site has a detailed history of his life. His mental state, as described in that article, makes him sound surprisingly like Morpheus: always away at war, no regard for his own life, ignores all commitments except to his kingdom. The ship is described in the second film as having the most rigorous duty schedule of any in Zion. Zion is, of course, the promised land. Google is where you can look up ridiculously easy-to-find things like who Osiris was.
My feeling on the connections between these names is that there aren’t really any except what you see on the screen. The names are borrowed from a hodgepodge of ancient times. I feel that the Wachowski brothers took a Dickensian view of naming people and things in their mythos: a name should tell you something (by reference if necessary), and it should also sound cool. In general, the story borrows the impact of these cultural icons and names to lend a certain gravitas and historical or legendary tone to the tale.