The documentation says:
Sets the language used for database
server warning or error messages.The language name can be 128
characters or less.
Which tells me zip about the actual format I’m supposed to use. Does it take a numeric LCID? A textual language name? In what format? en-US? English? Is it case sensitive? And so on.
And I presume “Current Language” and “Language” are equivalent for the purposes of that property?
connectionstrings.com says
So it will be one of the values you’d use for SET LANGUAGE which in turn comes from sys.syslanguages