The term first appears in 1695, although the design is much older. It was probably so called in reference to its "claws", which inflict parallel wounds. There are equivalent terms in many languages, usually strictly translating, and also some analogous terms referring to a similar instrument's number of tails (cord or leather), such as the Dutch zevenstaart (seven tail[s]), negenstaart (nine tail[s]) or the Spanish gato de nueve colas.
It traditionally has nine thongs as a result of the manner in which rope isplaited. Thinner rope is made from three strands of yarn plaited together, and thicker rope from three strands of thinner rope plaited together. To make a cat o' nine tails, a rope is unravelled into three small ropes, each of which is unravelled again.
Variations exist, either named cat (of x tails) or not, such as the whip used on adult Egyptian prisoners which had a cord on a cudgel branching into seven tails, each with six knots, used only on adult men, with boys being subject to caning, until Egypt banned the use of the device in 2001.
Sometimes the term "cat" is used incorrectly to describe various other punitive flogging devices with multiple tails in any number, even one made from 80 twigs (so rather a limp birch) to flog a drunk or other offender instead of 80 lashes normally applicable under shariah law. The closed cat, one without tails, was called a starter.