There are some names that sound posher than others to many class-conscious English ears. Essentially, it's whether they sound French - or rather, medieval Normam French - and therefore hint at ancestry among the Normal aristocracy who came over with William the Conqeror in 1066. De Bourgh, (or de anything) definitely counts here.

However, this undue regard for French-sounding names was sent out of kilter by the arrival of large numbers of French protestant huguenot refugees, who were often middle-class craftsmen. A very tentative guess: the names Lefroy and Darcy are a tad more likely to come from this source, since the Lefroys and the Darcy Wentworths were part of the Protestant domination of Ireland.

Nevertheless, they would still sound vaguely posher than obviously Anglo-saxon names.