This saying comes from ancient monks just before going out to slaughter some insolent people. Before the monks would leave they would say "be right back" in such a way it would imply they would be back in a few minutes but in actual fact they would be out for hours.
12:58 - Ancient Monk: gonna brb
12:58 - Ancient Ninja: kk
Ancient Monk is now Offline.
Ancient Monk is now Online.
21:40 - Ancient Ninja: Welcome back?
21:40 - Ancient Monk: Aye
21:40 - Ancient Monk: ;D
21:40 - Ancient Ninja: You just did a Foxhound