"AFK" looks vaguely familiar (is that the symbol of the concept/term, or am I so off, here, that it was just part of your describing the concept/term?), but I'm not remembering - or never knew - what it stood for i.e. re-presents.
But, whatever. The important thing is I got a tffb reply!
Away From Keyboard. Viewpoint that online life is the same to "in real" life. So instead of saying "irl" when referring to In Real Life, they say "when AFK". Or, instead of saying "oh I was not online" one would say "I was AFK".
Two rough examples
hello and good morning