The Jargon File (version 4.4.7, 29 Dec 2003):

Random Number God


    [rec.games.roguelike.angband; often abbreviated ?RNG?] The malign force
    which lurks behind the random number generator in Angband (and by
    extension elsewhere). A dark god that demands sacrifices and toys with its
    victims. ?I just found a really great item; I suppose the RNG is about to
    punish me...? Apparently, Angband's random number generator occasionally
    gets locked in a repetition, so you get something with a 3% chance
    happening 8 times in a row. Improbable, but far too common to be pure
    chance. Compare Shub-Internet.