Clarifications
The claim that the B. in Olivier B. Bommel would stand for Berendinus is semi-canonical at best. A middle name is not found in any of the original stories and —according to the author— did not exist. Bommel was intended to be an American, though it is possible that he did indeed return to ancestral grounds. The lone initial was part of the American attributes of the character. The source of Berendinus was the answer by an editor in the Tom Poes magazine, and thus one given with a semblance of authority, which explains the popularity of the claim.
Related to this is the play in the original series with the meanings of the Dutch word heer, which does mean gentleman, though it does not mean member of the nobility, which Bumble as American would not be, he is rich, very, very rich and tries to live like a gentleman. Another meaning is lord, as in (absolute) ruler, as owner of his castle he turns out to have been the lord of the land for almost the entire series in the last story. "Sir" rather obscures this essential part of the character as it rather suggests some noble title under lordship. An acceptable translation might be Oliver Bommel Esq.
Read more about this topic: Oliver B. Bumble