From the UK:
Why are Italian Americans referred to as ‘Guineas’ in films etc?
You picked that question as your first post?.. Ouch.
It’s slang. I don’t know the origin, but my guess is you’ll know soon.
Don’t know either, but to add my 2¢, the first time I ever heard the term used (and I’m almost 40) it was in the Christian Slater/Patricia Arquette (“True Romance,” I think), which was only a couple of years ago.
I assumed it meant “Eye-talians,” since that was whom they were referring to, and I thought it was funny–since it had no connection to the “guineas” that were familiar to me.
Guineas are a type of domestic fowl, similar to chickens, but a lot uglier–and they can fly a lot better.
If they get out of their coop, they’re gone.
Also, when I was a kid,I also had an uncle that used a phrase “I’d trade a gold guinea for . . . .”
I also thought that was funny, because I wondered "OK, a guinea made of gold would be worth a lot–but why would someone make a guinea out of gold.
I learned some years later that “gold guineas” were once coins of the British Empire.
I’d honestly be surprised if “guinea” was a recent coinage.
No luck on guinea, but “wop” has an interesting derivation, according to M-W:
Italian dialect guappo swaggerer, tough,
from Spanish guapo,
probably from Middle French dialect vape, wape weak, insipid,
from Latin vappa wine gone flat
Back off, man. I’m a scientist.
Alpha–
Didn’t mean to imply that I thought it was of recent vintage–just that I live in an area where there are no noticeable ethnic minority communities (other than Blacks); hence, there are no colorful ethnic slurs in common parlance–of course, with the exception of Blacks, and I think you’re probably already familiar with those colorful ethnic terms. 
FWIW – My tailor is an Italian-born woman (I refuse to call her a seamstress, that’s from another century) with the full-on accent and everything. She was telling me about her daughters one day. One wanted a nice, quiet wedding when the day came. The other told her dear sweet mom that she wanted a big loud Italian Catholic bash – a “guinea wedding” as she called it. It was so funny hearing this woman say “gheeny whedding” I almost peed myself.
I know that, in The Godfather, the source of all Italian knowledge for most of us, Sonny (Santino) Corleone calls his Italian-born wife a guinea. The line is, I believe, “Now, you guinea bitch, I’m gonna kill ya.” He proceeds to beat her with his belt and probably whatever else is handy. Sonny was not a nice guy.
I wonder if the term has anything to do with the place called Guinea, from which the island of New Guinea takes its name?
–Da Cap’n
“Playin’ solitaire 'til dawn
With a deck of fifty-one.”
Dave Wilton figured it got picked up by association. I find his explanation plausible, although I’d be interested in seeing some documentation:
http://www.wilton.net/wordorg.htm#Guinea
Tom~
Well I am sure that is older than any of those movies. I have relatives that occasionally use the term, most of the time joking around with a friend of theirs that is Italian. It does seem to have perjorative connotations.
For an added insult there is “swamp guinea greaseball” that was used where I grew up.
Godfather FYI: Santino Corleone didn’t beat up his wife, Carlo Rizzi beat up Connie Corleone who was his wife & Santino’s sister.
Thanks all…my first posting and look at all the attention I get. Love it…
“Heaven sends us good meat, but the devil sends us cooks”
David Garrick (1717-1779)
“Guinea” has been used for centuries as a name for a portion of west Africa - “the Guinea coast”. Calling Italians “guineas” implies they are not white people. Remember in the movie “True Romance” Christopher Walken plays a Sicilean gangster who takes umbrage at Dennis Hopper’s character’s suggestion that Sicileans are actually African. As with so many vulgar oral traditions we will probably never know who coined this ethnic slur.
((“TRUE ROMANCE” spoiler aler!!!))
Going along with the previous post, when Dennis Hopper’s character is “whacked,” two of the other thugs are talking. The conversation goes something like this:
1st thug: “Why did he ‘whack’ him?”
2nd thug: “He said Italians are descended from Blacks.”
1st thur: “Oh, OK.”