The online abbreviation "OMG" may conjure images of hyper-caffeinated teenagers caterwauling over instant messenger about who puked at the homecoming dance, but OMG has a much more distinguished pedigree.
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Perhaps the first usage of "OMG" appeared in a 1917 correspondence from British Admiral John Arbuthnot Fisher to Winston Churchill, wherein Fisher excitedly relayed the phrase to his former Royal Navy colleague — "I hear that a new order of Knighthood is on the tapis — O.M.G. (Oh! My God!) — Shower it on the Admiralty!!"
Look at sourpussed Fisher above. It's almost impossible to imagine him speaking the aforementioned sentence in anything but the voice of Alicia Silverstone circa 1995.
[Via Letters of Note and George Mason University]