According to TIOBE, Groovy rose from 0.33% to 1.8% in the last two months, and from 0.11% to 1.8% in the last 12 months. Click on "Groovy" from the main page and you'll get the graph at http://www.tiobe.com/tiobe_index?page=Groovy . Now say "maybe TIOBE's not that poor a measure of programming language popularity" with a straight face. These stats are gamed by language backers to make their language look good when selling consulting services and tickets to conferences, convincing programmers to contribute free work to their product, etc.
And yet, it is completely consistent with pretty much all other measurements of programming language popularity (github, job postings, StackOverflow answers, etc...).
So maybe it's not that poor a measure after all.