"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.
Me: It's a dog eat dog world out there.
Some kid: No it's not. It never was a dog eat dog world. Humans eat humans, but
dogs don't eat
dogs.
Me: My guy, you are so heavily misinformed. Dog eat dog isn't referring to
dogs, it's referring to humans.
Some kid: So why don't they just name it "human eat human" instead?
Me: Because context my guy, it's all about context. You see... "dog eat dog" actually belongs to the much older idiom "dog does not eat dog", indicating that
dogs never prey on their own kind. It took around 700 years for this idiom to become flipped and applied to humans.
Me: Also since you took it literally, I'll have you know that from an evolutionary standpoint,
dogs will eat other dogs if this is what ensures their survival.
