It's a wisdom tooth
you get them when you're old.
( Master Of Turnips. Only gays and morons believe in ghosts., Thu 9 Jul 2009, 11:50, archived)

Correct, but the other three have been present and correct since I was about 20.
I thought the fourth one had gone AWOL.
( Mr Gear the gay-maker, Thu 9 Jul 2009, 11:52, archived)