It's a Christian thing. It is thought by the Christians that Jesus was descended from the "House of David," although the Jews have other reasons for revering the great Biblical King. And don't forget that David (ostensibly) wrote the Psalms, so we have a musical hero here as well. I can see him now beside the still waters playing his lute and composing the Lord's Prayer.
I was told that the name means "beloved of God," but don't quote me on that. Makes sense, though. I had a Mexican friend named Telophilo, and he translated that as "David." "Philo" meaning love and "telos" meaning original cause, or God.
It's like the name Mohammed in Moslem countries: ubiquitous.
I thought about changing my username to something more interesting, but decided to just leave well enough alone.
"It's all right son . . . we told you what to dream"