Twists & Turns of Phrase
The last straw or final straw is a problem or annoyance that on its own would be a trifling matter, but that, when added to series of previous irks and irritations, seems intolerable.
This turn of phrase originated in the longer proverb the last straw breaks the camel’s back, a metaphor suggesting that there is a threshold to the burdens we can bear and that even the smallest additional burden beyond that threshold can break us.
This proverb can be traced back to Charles Dickens, who in his 1848 novel Dombey and Son wrote:
As the last straw breaks the laden camel’s back, this piece of underground information crushed the sinking spirits of Mr. Dombey. He motioned his child’s foster-father to the door, who departed by no means unwillingly: and then turning the key, paced up and down the room in solitary wretchedness. For all his starched, impenetrable dignity and composure, he wiped blinding tears from his eyes as he did so; and often said, with an emotion of which he would not, for the world, have had a witness, `Poor little fellow!’
Still earlier forms of this idiom have been traced to the 1600s and involved feathers and horses instead of straws and camels.