The last time Groovy made the top 20, it hit #18 in Oct 2013, but 3 months later (Jan 2014), had dropped back out of the top 50 (#32 in Nov, #46 in Dec). TIOBE said the following month "The data is produced by one of the sites that we track is interpreted incorrectly by our algorithms. After we fixed this bug, Groovy lost much of its ratings." [1] Just before that fix happened, interviews with the current Apache spokesperson for Groovy (Guillaume Laforge) promoting Groovy's top 20 position were published in 5 online rags (www.infoworld.com, www.eweek.com, cacm.acm.org, jaxenter.com, and glaforge.appspot.com), and all of them quickly appeared in Google's top 30 search results for "groovy programming" and remained there for 6 to 18 months afterwards. I'm guessing the same feedback effect was engineered again before the end of last month (Jan 2016), and Groovy will again start losing its new top 20 ranking.
This rapid rise then fall also happened with Groovy in December 2010. Groovy began a sudden rise from outside the top 50 when Groovy tech lead Jochen Theodorou "volunteered" his services to Tiobe in late 2010 to help them improve their algorithms. Than in April 2011, Groovy fell from #25 to #65 on Tiobe in a single month after they increased the number of search engines they monitor.
These fleeting peaks for Groovy in the TIOBE rankings (#25 in Apr 2011, #18 in Oct 2013, #17 in Jan 2016) between its usual ranking of somewhere between #51 and #100 (e.g. #82 only 12 months ago) are a bad thing for Groovy because of damage to its reputation as a solid language suitable for long-term IT solutions. Such ranking volatility gives off the stench of search engine optimization, a smoke-and-mirrors marketing tactic intended to benefit a single stake-holder, probably the person who privately owns the groovy-lang.org DNS domain.
[1] http://www.infoworld.com/t/application-development/c-pulls-a...