What is the origin of the idiom "the law of the jungle" and when to use it?

The idiom "the law of the jungle" originated from Rudyard Kipling's collection of stories called "The Jungle Book," published in 1894. Kipling used the term to describe the natural order and survival instincts observed in the animal kingdom, particularly in the jungle setting depicted in his stories. This phrase can be found in conversations about business, politics, sports, or social interactions, particularly when describing situations where individuals are driven by survival instincts, ruthless ambition, or a lack of ethical constraints.