Why not just expand the original query? A search for "devise ruby" works pretty well (https://duckduckgo.com/?q=devise+ruby).
I've long given up searching for trendily-named JavaScript libraries without adding "js" to the search term.
I've long given up searching for trendily-named JavaScript libraries without adding "js" to the search term.
(Edit- clarification re: ads)
Or, even better: "!rubygems devise".