Staley got cut.
The acronym has evolved to mean OLD NEWS.
Its definition is in reference to BYU running back Luke Staley who got cut from the Detroit Lions in 2003. Because he won the Doak Walker award in 2001 for college's best running back it was presumed he would have some sort of pro career but due to injury he got cut and quietly left the pro ranks. People unaware continually come to the board asking what happened to Luke? Who is he playing for?
When on a chat board and someone late to the party introduces old news:
The NFL Lockout is over!
SGC, see the thread 3 below.
When on a chat board introducing news and aren't sure if it has already been discussed:
SGC? Jimmer got drafted by the Kings.