A Dog's Breakfast

Recorded in British slang since at least the 1930s, first written down in Eric Partridge's landmark 1937 Dictionary of Slang and Unconventional English. The obvious logic is that dogs will eat whatever chaotic mixture of scraps they're given, making a "dog's breakfast" of leftovers a natural symbol for any messy jumble. Beyond that reasonable guess, though, nobody recorded exactly why this particular meal, rather than any other, became the go-to image for a muddle. A closely related but distinct phrase, "dog's dinner," emerged around the same period but took on an almost opposite meaning, describing someone dressed in an ostentatiously showy way ("done up like a dog's dinner"), which only adds to the puzzle of how the two near-identical phrases ended up pointing in such different directions.