One of the earliest modern memes, the British government put up signs that read 'Keep ______ And Carry On' in 1939, to inspire a sense of normalcy in the face of the impending World War 2. Fill in the one word blank, a sense of not being nervous.

The term meme was introduced in 1976 by British evolutionary biologist Richard Dawkins (author of "The God Delusion"). He conceived of memes as the cultural parallel to biological genes and considered them as being in control of their own reproduction.