Fluff/fluff one’s lines etc

To fluff something, as in to fluff a golf shot, or fluff a simple penalty shot in football or rugby, means to make a failed or inept attempt at something or other. The first known usage of this meaning derives from British theatrical language in the 1870s when to fluff one’s lines means to forget them. It is not known how or why this particular meaning of fluff came about. One suggestion is that it might be echoic of the verbal sounds an actor might make in trying to remember lines. The original meaning of fluff, of course, is any small piece of fabric or material that is very light, soft and downy, which meaning dates from the late 18th century. See also Bit of fluff.