Do You Call It Kitty-Corner, Katty-Corner, Or Kattywumpus?
First, let's make clear what we're talking about here. It's the word to describe two things that are opposite each other on a diagonal. If you're at the library, for example, and you cross the intersection diagonally (brave soul) to get to the post office on the far corner, then the post office is said to be kitty-corner, catty-corner, caddy-corner, or catawampus (or kattywumpus!) to the library. Which word do you use? Let's sort this out.
Both the Merriam-Webster Dictionary and the Associated Press Style Guide prefer the spelling kitty-corner. The Associated Press (AP) Style Guide is the authoritative style guide used by journalists and publishers. Kitty-corner is also the preferred term throughout most of the western and northern United States and Canada, according to a poll taken by author Mignon Fogarty, who writes under the name "Grammar Girl." The Dictionary of American Regional English backs this up, stating that "kitty-corner" is in common usage in the North, northern-Midwest, and West of the U.S. The exception to this kitty-corner preference is in the Southeastern United States. Let's cross on over there and learn what southerners call it.
It's catty-corner in the South
Catty-corner is the preferred term for that corner diagonally across from you, if you're in the southeastern portion of the United States. "Grammar Girl" Mignon Fogarty learned in her reader poll that the preference for catty-corner extends throughout the southeast, west to Texas, and as far north as Pennsylvania. Some poll-takers noted that the preference was hyper-regional, dividing states and even families apart. For example, one New Jersey resident used the term kitty-corner, while his wife opted for catty-corner. Another poll-taker admitted to converting from catty-corner to kitty-corner when she moved from New Jersey to New York.
Merriam-Webster's dictionary lists catty-corner as a less common variant of kitty-corner. No matter how it is spelled, the word is an adjective or an adverb, describing either an object, or how something is done. Additional accepted spellings include catty-cornered, kitty-cornered, and cater-cornered.
Caddy-corner is an unofficial variation of catty-corner which does not appear in the Merriam-Webster Dictionary. That is because, as Paul Brians, English Professor at Washington State University points out, it is a misspelling of catty-corner, an acceptable variation of the word.
What about cater-corner or catawampus?
If you can't decide between kitty- and catty-corner, you are welcome to say cater-corner. Historically, that's what people used to say, and according to the Merriam-Webster Dictionary, it's still an accepted variation of the expression meaning diagonally across.
"Cater" is from the French word "quatre," meaning four, according to the Columbia Journalism Review. In fact, "cater" is a historical term used for the four dots on dice. The dots are coincidently diagonal, or (pardon the phrase) cater-cornered from each other. Whether kitty-corner, catty-corner, or catercorner, all of these are American expressions, notes the Columbia Journalism Review. None are in common usage today in Britain.
Catawampus (also sometimes spelled with a "k" or as kitty-wampus) is yet another variation to the word known as kitty-corner, katty-corner, or cater-corner, according to the Dictionary of American Regional English. It also means askew. Though the origins of this variation is unknown, Merriam-Webster Dictionary writes that it is likely derived from the old English term catercorner.
Catawampus is one of the many terms documented by "Grammar Girl" Mignon Fogarty, including kiddie-corner, ketty-corner, and cat-corner. Fogarty suspects the multiple spellings come from people hearing the word and inventing the spelling on their own. However it is spelled or pronounced, if someone tells you the building is katty-corner or catawampus to you, look across to the diagonal and you will find it.