But I’m not carrying anyone’s golf clubs. And I don’t mean to be catty either, but did some writer or editor for Yahoo! Shine actually think this was correct:
Although I’m tagging this error as “Commonly confused words,” this is not an error that most English-speaking writers make. In fact, I’ve never known anyone to confuse caddy with catty. Never.
Terribly Write 
April 16, 2010 at 6:44 am
Tim Wood, who claims to be an editor for certain books, wrote in the b/r blog
” We assumed it was some kind of blonde versus brunette caddiness, and then we unearthed THIS photo.
Really? a writer? an editor? how embarrassing – this was linked from MSNBC. Can’t they at least make sure the articles they link to have been properly spell-checked.
April 16, 2010 at 7:11 am
Yikes! I don’t understand making this kind of mistake. Just what did the writers think “caddy” meant?
October 19, 2016 at 6:23 am
I’ve heard the phrase, too. I was about to use it in writing, and decided to search for the correct spelling and usage. I think the citation in the OP — and the sense I am planning to use — is that of being a “cad”. That is: “A low-bred, presuming person; a mean, vulgar fellow.” So “caddy” or “caddie” in this sense would mean “vulgar; base”. The meaning is distinct from “catty” (“subtle hostility”), but might be used in the same general situation where someone is “not using polite or socially acceptable speech”.
October 19, 2016 at 7:24 am
That’s a charitable view. However, I can’t find an authority that allows “caddy” (or worse, “caddie”) as the adjectival form of “cad.” The dictionaries I’ve consulted all offer “caddish” as the adjective. Further, in some dictionaries, a cad is always a male; I think in the reader’s mind the connotation of the word is male also. So, I just don’t see “caddy” working in the excerpt above nor in your example.
October 19, 2016 at 7:45 am
I agree that I couldn’t find any online dictionary give the adjective form “caddy” or “caddie”, so I would definitely not consider this standard usage. Nor can I say I find this phrase common. But I do believe I have heard it in this sense, and it is a plausible formation from “cad” in casual speech.
Google Ngram shows phrases with “cad” peeked in the 1920’s: https://books.google.com/ngrams/graph?content=be+a+cad%2Csuch+a+cad%2Cis+a+cad&case_insensitive=on&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t4%3B%2Cbe%20a%20cad%3B%2Cc0%3B%2Cs0%3B%3Bbe%20a%20cad%3B%2Cc0%3B%3Bbe%20a%20CAD%3B%2Cc0%3B.t4%3B%2Csuch%20a%20cad%3B%2Cc0%3B%2Cs0%3B%3Bsuch%20a%20cad%3B%2Cc0%3B%3Bsuch%20a%20CAD%3B%2Cc0%3B.t4%3B%2Cis%20a%20cad%3B%2Cc0%3B%2Cs0%3B%3Bis%20a%20cad%3B%2Cc0%3B%3Bis%20a%20CAD%3B%2Cc0