The term 'OMG' (Oh My God) was first used in writing in 1917 in a letter sent to Winston Churchill.
Why it is true
Admiral Lord Fisher wrote it to Churchill to express his shock about a new order of Knighthood, showing that internet slang existed long before the internet.
Source: Linguistics
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.