It's a joke. An older version of the joke, from Usenet, is that RTFM stands for "Read The Manual".
The gag is that the newbie asking the question will wonder why the F wasn't included in the expansion, and rapidly figure it out. Or they ask, and you make fun of them for it. The joke is either kinda cerebral or really juvenile... and the tension between the two is part of the joke.
DFE "deleted everything"