"A dog's breakfast is any kind of smorgasbord prepared, in haste or at random, from life's castoffs... The slang lexicographer Eric Partridge cited Glasgow circa 1934 as its place and time of origin, though he noted that Australians also used the phrase with the same meaning as "confusion, mess, turmoil."The derivation summarized: "Although the origin isn’t exactly known, it alludes to the fact that if what you don’t succeed at what you are cooking, then the results are only fit for a dog... It is suggested that this dates from a time before canned dog food when a pup’s breakfast would have consisted of dinner leftovers from the night before; hence, “a mess.”
About the same time, a dog's dinner appeared with a quite different sense. "Why have you got those roses in your hair?" asked a character in "Touch Wood," a 1934 novel by C. L. Anthony. "You look like the dog's dinner ." This expression was defined by the Oxford English Dictionary Supplement as "dressed or arranged in an ostentatiously smart or flashy manner," probably derived from the 1871 usage "to put on the dog ."
And then there's "dog's bollocks," used to connote absolute excellence.
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