well, dog my cats

well, dog my cats

An expression of astonishment. “Dog” may have been euphemism for “damned,” as in “I'll be doggone.” “Cats” might have been just something opposed to “dog.” The earliest written reference is in O. Henry's 1910 short story, Memoirs of a Yellow Dog: “I began to feel sorry for Hubby, dog my cats if I didn't.”
See also: cat, dog