"Bright Young Things", from the alternate title of Evelyn Waugh's 1930 novel Vile Bodies about affluent
London glitterati/party-goers (a
la Hiltons/Lohans but slightly less illiterate)
Now, via analogy to MJ hit "PYT" the abbreviation has been applied in a wider sense beyond celebutantes, to wit, the little valedictorian darlings from Stanvard or Yalumbia who see it as their birthright to be rulers & managers of the universe but lack information about other walks of life, have never lifted anything heavier than a bookbag or
lacrosse stick, and are otherwise prestigious before their
time. Often found at
TED conferences, Park City trade conventions, in Barcelona/Prague/Copenhagen for years abroad, in the U.S. DOJ, or at their apartments watching Rachel Maddow, 30 Rock, True Blood, Deadwood, Big Love, Entourage (basically anything from the
HBO Time Warner production office is catnip to them)