Dog eat dog

"Dog eat dog" is analogous to the idiom "every man for himself", which implies a situation in which fierce deadly competition is necessary for your survival. Some of these recent definitions seem to be offended at this saying due to their ignorance of the origin behind this 500 year old idiom. Some people do not seem to realize that this idiom is NOT meant to be taken literally. So, why is it called "dog eat dog" you may ask? Well, the idiom is actually a play on the much older latin idiom "dog does NOT eat dog" (canis caninam non est), which originated as early as 43 BC and first spoken by Roman scholar Marcus Tarentius Varro. "Dog does not eat dog" is a proverbial saying indicating that even animals are better than humans in that they don’t prey on their own kind. The phrase entered into English discourse in 1543. Eventually, the phrase got flipped and applied to humans and henceforth "dog eat dog" was born. Both idioms generally imply the same thing (that humans are capable of being merciless). So to summarize, the idiom "dog-eat-dog" is derived from its parent idiom "dog-does-not-eat-dog". The latter idiom makes sense in and of itself, while the former idiom ONLY makes sense in relation to its latter.