Thomas1 said:
Therefore, would you say it's not used because it is obsolete or it is a kind of word that people don't use since it's quite offensive?
In American English (and elsewhere too, I believe) there is an IMMENSE vocabulary of these words. They can still be used among friends (particularly male) in a humorous, joking way - which invites the same type of response to the other person's ethnicity. Otherwise, they are always offensive and insulting, as are those who still use them. One caveat: such words referring to black people and to Jews can NEVER be used, even jokingly or humorously in the U.S., without stamping the user as a racist. Enough is enough.
Some of these ethnic designations have been used in the past, always demeaningly, as adjectives and can be found in some authors of the '20s, '30s and '40s, and in Hollywood "B" films:
They came out with a big jug of Dago red.
(Cheap red wine - from California or Italy.) These uses are also rude and impolite.
Other such, for Italians: wop (supposedly an immigration abbreviation for: Without papers, written: w/o p, but I have heard other derivations), guinea (upon its creation, the Verrazano bridge in New York, which, viewed from a local level, links an Italian-American neighborhood in Brooklyn with Staten Island, the most Italian-American borough, was known locally as the "Guinea Gangplank" - even more so after the film "Saturday Night Fever"); greasers, greaseballs (also used for Hispanic Americans).
These words should be avoided by all and sundry, whether native speakers or not, as should words like: "honkie" and "cracker." Almost all of them qualify as "fighting words," i.e., their use is a legal justification for striking the person using them and will excuse, in court, any injury (short of permanent maiming or death) the user may suffer in consequence. The same holds true of vulgarities used to describe homosexuals.