After someone or something has experienced a series of recurring offenses or problems, even a minor one can be the one that causes one to finally lose patience or for something to stop working. It alludes to the idea that a single additional piece of straw could cause an overladen camel to finally collapse. Common versions of this phrase are "the last straw" and "the straw that broke the camel's back." A: "Why are you furious now? Tom's been taking credit for your ideas for years." B: "It is the last straw that breaks the camel's back!" I've hiked miles and miles in these boots—I can't believe they finally fell apart while I was walking in my own driveway! But I guess it is the last straw that breaks the camel's back.