Some software and websites show (or showed) a little country flag for each language. For example, German would get the flag of Germany. Don't do this. It is flawed for so many reasons...

Here's a whole blog about this, by someone who cares about it more than me:

https://www.flagsarenotlanguages.com/blog/

Thanks for the link - they do a good job of addressing it from many angles.

There are these two letter symbols https://en.wikipedia.org/wiki/List_of_ISO_639_language_codes

I suppose a major issue here is I wonder how many people who speak Irish know that's abbreviated to "ga"

Yep. Then there are the second level codes such as en-us (American English) not to mention whatever you write to denote the differences between Chinese in various dialects written in simplified or traditional characters or the various non-Chinese languages in China that may be written using Chinese characters or with some other characters such as Roman or Cyrillic.

Thus the system is obscure to the layman but for the pro or serious amateur you find the standard is not well defined at all.