this.Language is the language subtag (ISO code) for the writing system.  This is often an abbreviation of the language's name ("en" for English, "de" for German, etc).  But when it's an unlisted language ("qaa"), it has no relation to the language's name.  Our convention of adding a language pseudo-subtag in the private use area comes into play since it will be derived from the initial letters of the language's name.
In any case, Language will always return a string that is either 2 or 3 letters long.