I propose and request as an enhancement that the BIP 39 wordlist set 
should specify canonical native language strings to identify each 
wordlist, as well as short ASCII language codes.  At present, the 
languages are identified only by their names in English.

Strings properly vetted and recommended by native speakers should 
facilitate language identification in user interface options or menus.  
Specification of language identifier strings would also promote 
interface consistency between implementations; this may be important if 
a user creates a mnemonic in Implementation A, then restores a wallet 
using that mnemonic in Implementation B.

As an independent implementer who does not know *all* these different 
languages, I monkey-pasted language-native strings from a popular wiki 
site.  I cannot guarantee that they be all accurate, sensible, or even 
non-embarrassing.

https://github.com/nym-zone/easyseed/blob/1a6e48bbdac9366d9d5d1912dc062dfc3f0db2c6/easyseed.c#L99
```
	LANG(english,			u8"English",	"en",	ascii_space ),
	LANG(chinese_simplified,	u8"汉语",	"zh-CN",ascii_space ),
	LANG(chinese_traditional,	u8"漢語",	"zh-TW",ascii_space ),
	LANG(french,			u8"Français",	"fr",	ascii_space ),
	LANG(italian,			u8"Italiano",	"it",	ascii_space ),
	LANG(japanese,			u8"日本語",	"ja",	u8"\u3000"  ),
	LANG(korean,			u8"한국어",	"ko",	ascii_space ),
	LANG(spanish,			u8"Español",	"es",	ascii_space )
```

Per the comment at #L85 of the quoted file, I also know that for my 
short identifiers for Chinese, “zh-CN” and “zh-TW”, are imprecise at 
best—insofar as Hong Kong uses Traditional; and overseas Chinese may use 
either.  For differentiating the two Chinese writing variants, are there 
any appropriate standardized or customary short ASCII language IDs 
similar to ISO 3166-1 alpha-2 which are purely linguistic, and not fit 
to present-day political boundaries?

My general suggestion is that the specification of appropriate strings 
in bitcoin:bips/bip-0039/bip-0039-wordlists.md be made part of the 
process for accepting new wordlists.  My specific request is that such 
strings be ascertained for the wordlists already existing, preferably 
from the persons involved in the original pull requests therefor.

Should this proposal be “concept ACKed” by appropriate parties, then I 
may open a pull request suggesting an appropriate format for specifying 
this information in the repository.  However, I will must needs leave 
the vetting of appropriate strings to native speakers or experts in the 
respective languages.

Prior references:  The wordlist additions at PRs #92, #130 (Japanese); 
#100 (Spanish); #114 (Chinese, both variants); #152 (French); #306 
(Italian); #570 (Korean); #621 (Indonesian, *proposed*, open).