Thanks, everyone, for the help! The OneLook Reverse Dictionary and RhymeZone’s “related words” were both extremely helpful.

AnnaStrophic, I had been to the Visual Thesaurus before, and while I love its interface, I just can’t bring myself to buy a subscription!

Jackie, sorry for the confusion. Perhaps I should have said “indirectly related” instead of “closely related.”

And Hydra, the Word Finder sounds promising. Best of luck in tracking down your analog copy! Know of a digital version?