(1) Old English phoulcat (foul cat). Originally a reference to the fitch, the wild ancestor of the domesticated ferret, because of their ability to emit a foul smelling spray when frightened. (2) Later, used in North America as a reference to the skunk. Both are actually not cats, but members of the weasel family, Mustelidae.
The symptoms of withdrawal can last for a few days up to a few weeks. It really is dependent on each person and their personal addiction. The most common withdrawal times usually last somewhere between a week and 14 days.
To the best of my knowledge (and I'm not a doctor, though I have some experience in the matter) the worst of it should be over in about two weeks (possibly four or five days), though I suppose that depends on how high of usage you have maintained and for how long. You should be more or less completely over the withdrawals in a month or so.