I don't think stackoverflow is a particularly useful metric. If there is a simple easy to use and install language with good documentation, examples and a forum

I don't think stackoverflow is a particularly useful metric. If there is a simple easy to use and install language with good documentation, examples and a forum/mailing list with a small number of new users, it will be much lower on an equally as popular language with complex syntax and no community with a larger proportion of novice users. Stackoverflow really fills the gap if there is no good alternative, it's a reflection of the ecosystem around the language than its popularity. Perhaps the number of new projects or commits in a given language would be more indicative of a language's true popularity. (Not that it's a perfect metric either)