Today’s idiom: the straw that broke the camel’s back
Meaning: reaching the limit of what you can endure
Origin: It seems that the origin of this phrase is very circuitous, not at all starting with a camel, or any straw. In ancient Rome there was a saying by Seneca, “It is not the last drop that empties the waterclock, but all that has previously flowed out.” John Bramhall said in the 1600’s, “It is the last feather that breaks the horse’s back.” The most famous and earlier version most similar to the one above was written by Charles Dickens in his 1848 book Dombey and Son, “As the last straw breaks the laden camel’s back, this piece of underground information crushed the sinking spirits of Mr. Dombey.”
Source: yahoo voices.