More specifically, it's in Names.php.

Upstream bug http://unicode.org/cldr/trac/ticket/5544 has been closed as INVALID, with the following rationale:

No locale for nap in cldr - invalid.

As the language isn't in the CLDR, we need a strong source for the language name.

http://scholar.google.com/scholar?q=Nnapulitano doesn't especially provide relevant work. http://scholar.google.com/scholar?q=Napulitano neither.

Is there any Neapolitan reference book (a grammar, a dictionary for example)?

(In reply to comment #2)

Upstream bug http://unicode.org/cldr/trac/ticket/5544 has been closed as
INVALID, with the following rationale:

No locale for nap in cldr - invalid.

---

As the language isn't in the CLDR, we need a strong source for the language
name.

http://scholar.google.com/scholar?q=Nnapulitano doesn't especially provide
relevant work. http://scholar.google.com/scholar?q=Napulitano neither.

Is there any Neapolitan reference book (a grammar, a dictionary for example)?

I don't know about a book, but someone else (whose native languages are listed as French and Italian) also agrees: see https://nap.wikipedia.org/w/index.php?title=Utente_chiàcchiera%3APiRSquared17&diff=606009&oldid=603019 (the first part is Italian, the second French). How much of a source do we need? Some less-reliable sources like Wikibooks claim it. t's usually a spoken language, so finding a reference book may prove challenging. However, I believe some reliable source may be found.

(In reply to comment #3)

How much of a source do we need?

This is explained in https://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sources

maximeemery94 wrote:

I've a high knowledge of the Neapolitan language and I'm sure that we don't write "Nnapulitano" but "Napulitano", so the name might be changed. If you look at this page,
[https://nap.wikipedia.org/wiki/Napulitano], you can see that the name of the language is "Napulitano", but when there is the article "'o" in front, we write "Nnapulitano". It was just my opinion about this subject.

Personal opinions are okay, but as written before we need reliable sources.

Confirmed both for adjective and noun on: Dizionario napoletano : italiano-napoletano, napoletano-italiano / [a cura di Bruno Amato e Anna Pardo]. - Rist. - Milano : Vallardi, 2009. - 293 p. ; 15 cm.

It's just a small dictionary they have in the closest local library, but should be enough: 1) it's common behaviour in Italian language(s), [[w:it:Raddoppiamento fonosintattico]]; 2) usage confirms, https://www.google.it/search?tbm=bks&q=%22Napulitano%22 vs. https://www.google.it/search?tbm=bks&q=%22Nnapulitano%22 containing only occurrences preceded by vowel or from pseudo-Latin texts of 18th century or earlier.

maximeemery94 wrote:

(In reply to comment #7)

Confirmed both for adjective and noun on: Dizionario napoletano :
italiano-napoletano, napoletano-italiano / [a cura di Bruno Amato e Anna
Pardo]. - Rist. - Milano : Vallardi, 2009. - 293 p. ; 15 cm.

It's just a small dictionary they have in the closest local library, but
should
be enough: 1) it's common behaviour in Italian language(s),
[[w:it:Raddoppiamento fonosintattico]]; 2) usage confirms,
https://www.google.it/search?tbm=bks&q=%22Napulitano%22 vs.
https://www.google.it/search?tbm=bks&q=%22Nnapulitano%22 containing only
occurrences preceded by vowel or from pseudo-Latin texts of 18th century or
earlier.

You can see that there are much more results for "Napulitano" than "Nnapulitano" and that the results with "Nnapulitano", except the first, makes no sense (if you read the sentence in which it is).

(In reply to comment #8)

You can see that there are much more results for "Napulitano" than
"Nnapulitano" and that the results with "Nnapulitano", except the first,
makes
no sense (if you read the sentence in which it is).

Indeed, and the first result you mention is not a reliable source (student thesis).

maximeemery94 wrote:

(In reply to comment #9)

(In reply to comment #8)

You can see that there are much more results for "Napulitano" than
"Nnapulitano" and that the results with "Nnapulitano", except the first,
makes
no sense (if you read the sentence in which it is).

Indeed, and the first result you mention is not a reliable source (student
thesis).

So, can we change "Nnapulitano" to "Napulitano" or we need more sources (I think that we can clearly see that the good one is "Napulitano"...

Hi. Can someone please update Names.php to reflect this, per the recent comments?

Are there any exact guidelines for this? Will this be fixed?

Change 76289 had a related patch set uploaded by Nemo bis:
Change name of Neapolitan language from "Nnapulitano" to "Napulitano"

https://gerrit.wikimedia.org/r/76289

Change 76289 merged by jenkins-bot:
Change name of Neapolitan language from "Nnapulitano" to "Napulitano"

https://gerrit.wikimedia.org/r/76289

Thanks.