A
whip with nine
lashes. Originally called
cat, probably because of its
ability to '
scratch' the
victims.
It was believed that the whip should have exactly nine lashes, because being punished by a 'trinity of trinities' can be seen as pious, sacred and more efficacious.
However, whips with a lesser number of tails certainly existed. For example, a criminal called John Lilburn was scourged in 1637 with a whip having only three lashes, but to compensate, each tail had twenty knots, and the culprit was struck with the whip every three paces between the Fleet and the Old Palace Yard of London.
During the reign of James II, Titus Oates received as many as 17000 lashes from a whip with nine tails (ouch!) on his way to Tyburn, according to a contemporary report.
The cat o'nine tails was once used by the British Army and Navy to punish offenders, but has since fallen into disfavour, just like some other forms of corporal punishment (see execution, lynching, dismemberment etc).
See also American Old Navy discipline.