The term comes from a famous soliloquy given by Macbeth in Shakespeare's play. It can be used to dismiss a person's action or argument as irrelevant or futile.
'Life's but a walking shadow, a poor player
That struts and frets his hour upon the stage
And then is heard no more: it is a tale
Told by an idiot, full of sound and fury,
Signifying nothing.' -- Macbeth