Today's OED antedating: "dog-eat-dog"

Dog-eat-dog, figurative, ruthless environment ("dog," n.1, sec 20, first use cited 1931): Book titled The Short-Stop, by Zane Grey, 1909, ch vii, p 109: "On the field ball-playing is a fight all the time. ... Every man for himself! Survival of the fittest! Dog eat dog!"