@RobDog it comes from a prompt in a Call of Duty single-player campaign mission where you "pay your respects" to a deceased soldier by pressing a single button. The very concept of putting such a thing in a video game was so ridiculous as to ne farcical, and a screenshot from the PC version (where the F key is the "interact" or "use" button) displaying the "Press [F] to show your respects" prompt was widely circulated and mocked. Now folks on the 'net often "press F" to pay their respects to a "fallen" comrade, whether sincerely (like when a streamer dies in a game) or ironically (as in this case).