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1.
For the sake of fuck.

FFS = "for fuck's sake", NOT "for fuck sake".

And, "for fuck's sake" = "for the sake of fuck". Just as "for Pete's sake" = "for the sake of Pete", or "for goodness' sake" = "for the sake of goodness".
Stop typing "for fuck sake", FTSOF!
by The Spelling Fairy October 23, 2009