These are the references I could find ..
here is a discussion reference and an included further references .. I think, this might the standard followed by ms in sql server.. but, then again , a guess 😉
Thanks for your digging, Demonfox! Much appreciated.
The first reference is to a standards body. I would not automatically assume that Microsoft adheres to any standard they didn't invent themselves. 😉 And indeed - I checked the ENU code that is rlevant to this discussion, and it's not included in the list.
The second link is a discussion on the non-standard nature of the three-letter codes used by MS, and the third reference lists a C# program one could use to output the list from Windows. The cropped output shown shows that, at least for American English, SQL Server does not use the code listed as "ISO", but does use the code listed as "WIN".
I'm not sure if that means that I could run that program and use the entire list for my Thesaurus files, as I still have not seen a reference telling me that the three-letter code used by full-text search is always equal to that "WIN" code. Or that all languages in that output are supported by full-text search. Or that that list includes all supported languages. And even if that all would be the case, then I still maintain what I previously replied to Tom - this information should be included in Books Online, in a place that is easy to find, and in the form of a table listing all supported languages and the corresponding three-letter code. Not in the form of a program I'd have to copy, paste, compile and run first. In my opinion, Microsoft really dropped the ball here.