So in my world there are 3 groups of people based off different types of puppets. Marionettes, stick-and-rod, and Ventriloquist dummies. Each of them have a nickname (puppet, rod, dummy). Yes, I know dummy seems strange but I couldn't think of anything else. When plotting this story I've run into a problem--How would I write the plural of dummy? Would they be dummies or dummys? Since dummy is not an official name and only a nickname I'm betting on dummies, but I would like to have a second opinion.