I believe it's an evolution of a reference from one of the Call of Duty games. In the game you literally press F to pay respects at one point. Pretty sure it was memed to death and then evolved from there

It also is commonly used sarcastically

same here. Had RiF before I had a reddit account because a friend of mine told me to check it out. Really sad to delete it

lol I had no idea it had a real wiki page