“Keep your eyes peeled” means to keep your eyes wide open, to keep a sharp lookout, to stay alert.
One form of this expression, “keep your eyes skinned” was used on the frontier and recorded in 1833, in the Encyclopedia of Word and Phrase Origins by Robert Frederickson: “I wish I may be shot if I don’t think you had better keep your eyes skinned so that you can look powerful sharp.”
One theory for the origin of the phrases is that it comes from the early days of the British police. In 1829, Home Secretary Sir Robert Peel, established the Metropolitan Police Force in London, the first professional police force. Before long the policemen had picked up the nicknames “Peelers” and “Bobbies” for the unpopular fact that they reported directly to Peel at the Home Office. “Bobbies” is still a friendly nickname for the police in England. “Peelers” is not used but may have left its mark in the expression to keep your eyes peeled, as per their founder’s instructions.
WorldWideWords has the following explanation:
It derives from an old verb pill, “to plunder,” which is the root of our modern word pillage. It came to us from the Latin root pilare, meaning “to take the hair off, to pluck” (closely connected with our “depilate”), but which also had the figurative meaning of “plunder, cheat,” almost exactly the same as the figurative meaning of our modern verbs “fleece” or “pluck.” From about the 17th century on, “pill” was commonly spelt “peel” and took on the sense of “to remove or strip” in the weakened sense of removing an outer covering, such as a fruit. The figurative sense of keeping alert, by removing any covering of the eye that might impede vision, seems to have appeared in the US about 1850.
Although probably not the first use, in 1853, The Daily Morning Herald in St Louis wrote, “Young man! Keep your eye peeled when you are after the women.”
Good advice, I think. Very practical.
I keep my eyes peeled and my mouth open when it comes to food.