"a tale told by an idiot"

This phrase comes from Shakespeare's Macbeth.

Macbeth, having lied and killed his way to the top, learns that his wife is dead as he is preparing for battle. Faced with the loss of the woman he loves, life loses all meaning for him:

 

MACBETH

She should have died hereafter;
There would have been a time for such a word.
To-morrow, and to-morrow, and to-morrow,
Creeps in this petty pace from day to day
To the last syllable of recorded time,
And all our yesterdays have lighted fools
The way to dusty death. Out, out, brief candle!
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.