Well, the link Rusty provided gives several hypotheses, saying that it is used on a regional basis in America, England, Australia, and other predominantly English-speaking countries...
I'd think it may have been originally coined at a verbal level, not finding its way into the BNC, but I am just guessing.
Someone should take full responsibility and research this matter six ways to Sunday and come up with a fully authoritative answer...
(I'd bet it was the Canterbury Archdeacon who said it once while drinking tea...) (But I wouldn't bet much, honestly.)
