1911 Encyclopædia Britannica/Poach

POACH (probably from Fr. poche, bag, or Eng. “poke,” thrust into), to trespass on private property in pursuit of game or fish; also, generally, to catch game or fish by means or at times not permitted by the law, or in an unsportsmanlike manner (see Game Laws). The etymology is rather obscure, but as used in the independent sense of “poaching” an egg, i.e. cooking by breaking into boiling water, the word appears to be from the same original.