it's a word from which sprang a lot of sayings. I wonder why. From the 1873 slang dictionary:
Dogberry, a foolish constable.—
Shakspeare.
Dog cheap, or DOG-FOOLISH, very or singularly cheap, or foolish. Latham, in his
English Language, says:—“This has nothing to do with dogs. The first syllable is god=
good, transposed, and the second, the ch‑‑p, is chapman, merchant: compare EASTCHEAP.”—
Old term.
Doggery, nonsense, transparent attempts to cheat.
Dog gone, a form of mild swearing used by boys.
Dog in a blanket, a kind of pudding, made of preserved fruit spread on thin dough, and then rolled up and boiled. This pudding is also called “rolly-polly” and “stocking.”
Dog in the manger, a scurvy, ill-conditioned, selfish fellow. From the fable of that title.
Dog Latin, barbarous Latin, such as was formerly used by lawyers in their pleadings. Now applied to medical Latin.
Dogs, TO GO TO THE, to be commercially or socially ruined. Originally a stable term applied to old or worthless horses, sold to feed hounds.
Dog’s body, a kind of pease pudding.—
Sea.
Dog’s ears, the curled corners of the leaves of books, which have been carelessly treated. The use of this term is so common that it is hardly to be considered slang.
Dog’s nose, gin and beer, so called from the mixture being
cold, like a dog’s nose.
Dog stealer, a DOG DEALER. There is sometimes less difference between the two trades than between “d” and “st.”
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There's also "dog-tired' and "f*cking the dog" (to be lazy)