Google it if you have to, but it is generally advisable to know what their meanings are. Or other connotations. Because just because you don't know what the meanings are, doesn't mean they aren't meaningful names when you use them in the right situation. If you decide that your hero Thomas will turn out to have an Evil Twin, the choices are renaming him and having people say, Oh yes Thomas means twin so that was a clue there. There may not be many of them -- the same stuff which ensure many readers will not pick up on intentional Meaningful Names will also protect them against accidental ones -- but they will exist.
Last names are worse because a lot of them wear their meanings on their sleeve: Greene, Smith, Meadows, etc. Some don't, of course, but it's a lot harder to fill up the list without any of them. And worst of all is when a first name vaguely suggests something, and the last name is needed that harmonizes without pushing the whole thing over the top.