Should Bob have been called Bill? That can depend on many things, such as period, who/what Bob is, names of other characters etc. I, personally, set a lot of score by names when writing my stories. Whenever possible, I like to assign names that represent the character's personalities or their roles within the story. I also try to keep names distinct from one another within any given piece to avoid confusion for readers.
My favourite sites for name meanings are:
First Names: Behind the Name and Meaning of Names
Surnames: Behind the Name
In speculative fiction, where there is even more flexibility, you can also create names. I've done this at times, but I still base those names on an idea I want to convey. Say I have a Slavic-type evil vampire leader. I might forge a name for him using as my basis the Czech word for 'dark' or 'threat' or 'torment'. Meanwhile, the hero's name could be based on the word for 'noble' or 'valiant' or 'pure'.
Names are one of the first things I consider when commencing a new story. Once I have the initial idea and know the cast of characters I need, I research and plan their names before setting a single line down.
What's in a name? Often quite a lot of hidden meaning.