Is this 1917 letter to Winston Churchill the first documented use of ‘OMG!’?

Is this 1917 letter to Winston Churchill the first documented use of ‘OMG!’?:




Moon Unit Zappa, eat your heart out: It’s being said ‘round the Internets that this letter, dated September 9, 1917 by Lord John Fisher to Winston Churchill, is one of the first documented uses of the teenybopper expression “OMG!”

Via The World’s Best Ever