dog my cats! An expression of surprise.
R. Berg offers this speculation from the other side of the pond as posted in The Phrase Finder in 2001: “My first take on this was that its form suggested 'Damn my soul' minced very fine, enriched by the idea of cursing oneself by wishing a dog set on one's cats, and that it wouldn't be in the books.” Well, as it turns out it is in books, at least in the US.
The most familiar reference for American readers is likely to be in The Adventures of Huckleberry Finn. On page four, Jim says, “Say — who is you? What is you? Dog my cats ef I didn' hear sumf'n.” In this context it sounds almost like a curse, as in “damn my soul should I turn out to be wrong.” But later in the book, Jim uses the turn of phrase again without quite the same implications, at least to my reading.
1. Berg, R. 2001. Re: “Well, Dog My Cats!” Phrase Finder. Sheffield Hallam University. Accessed May 30 2006 from http:// www.phrases.org.uk/ bulletin_board/ 9/messages/ 24.html.
2. Twain, Mark, and Michael Patrick Hearn. 2001. The Annotated Huckleberry Finn: Adventures of Huckleberry Finn (Tom Sawyer's Comrade). New York: Norton.
3. Ibid. 149.