So I thought, let's find out! M. mentioned Ralph Waldo Emerson, and he's recent and every conceivable aspect of his life has been analyzed to death, so I figured it'd be pretty easy to figure out where he got the middle name Waldo.
But don't go here, because that's just an utter bunch of crap.
They think he got it from Peter Waldo, a religious preacher from Lyons in France a long while ago. We'll be coming back to Peter in a bit, but let's stay focused on Ralph for now.
According to his wikipedia entry http://en.wikipedia.org/wiki/Ralph_Waldo_Emerson, "He was named after his mother's brother Ralph and the father's great-grandmother Rebecca Waldo." That sounds plausible, at any rate. Who was Rebecca Waldo, then? I figure, we're talking a bunch of of New Englanders, _someone_ has done the genealogy. And indeed, they have. Waldo Lincoln wrote it a while back and you can read it for free or download it or print it out or whatever:
In that, we learn pretty quick that Cornelius Waldo (the immigrant) had a daughter named Rebecca who married one Edward Emerson. I'm not happy about this loose of a match, but since what I _really_ want to know is the origin of the name Waldo, I'll take it.
So where did Cornelius Waldo come from? The author of that book thought maybe England, but didn't make any progress with the theory, and honestly, I'm kind of suspicious of that theory. So we'll put Cornelius on hold for a minute and go back to Peter.
Really? You're honest to God going to convince me there was a merchant turned preacher in _Lyons_ with the name _Waldo_? What do the French think of this theory? They don't really have a "w" in their language, and words that would otherwise have a "w" fall into two categories: the "ou" category (like my husband's last name, which is French-Canadian and, we suspect, originally a Dutch surname that got Frenchified) and the "v" category. Pierre is the latter, but the editors of French Wikipedia seem every bit as confused about his name as I find myself; they take pains to tell us what that name _isn't_, a sure sign that no one knows what's going on.
So we now have a "merchant" in Lyon named Waldo and a guy named Cornelius, so despite the location of Lyon in central France I'm going to adopt the theory that Waldo is, in fact, Germanic.
This suggests that Waldo [ETA: and I don't mean here any particular Waldo, but rather an abstarct early bearer of the name] is actually Waldemar and possibly, originally, Vladimir and Slavic.
But I'm open to suggestions, because the evidence here is unbelievably weak.