A bit of the ole Ralph Nadar effect going on here, I presume. Java's share is being cannibalized by Groovy, Scala, Clojure, etc. They should start making a JVM ranking to start consolidating all those languages.
Yes, I understand those are frameworks not languages. The point was that since TIOBE indexes against the word 'javascript' and not 'node,' etc. I think it's possible that JavaScript's relative usage is obscured.
This is purely anecdotal on my part but it seem to me I see many posts or articles talking about 'writing an app in node.js' or 'the UI was written in jQuery' rather than 'written in JavaScript.' This seems to me a phenomena more or less unique to JavaScript.