Great news! On the About page, you can always find listed the tools which have been created for this project. As of yesterday, Tech Support added Concordance-Reversed.py to the Digital Humanities Toolkit.
Concordance.py will take your text and strip out a set of Stop Words. It’s what I used to strip out the Ten Thousand most common words from The Hobbit.
Concordance-reversed.py will strip out everything but a set of Go Words! It’s what I’m using now to find specific lemmas, such as Fish, Fishes, Fish’s, Fishes’, Fished, Fishing. Put all the different forms of your lemma into a text file of Go Words, and you’re on your way!
I love you, Tech Support, from your grateful Mama.