It isn’t just a meme. As KnowYourMeme points out, it comes from Richard Stallman. Wikipedia has a good article about it here.

The term GNU/Linux is promoted by the Free Software Foundation (FSF) and its founder Richard Stallman. Their reasoning is that the GNU project was the main contributor for not only many of the operating system components used in the subsequent development of modern “Linux” systems, but also the associated free software philosophy.