While Napoleon Hill is credited with inventing the term “mastermind” to denote a group of peers who met regularly to give each other advice and support, he got the term from Andrew Carnegie, who credited his entire fortune to his mastermind group. And if you think masterminds are just for business, you haven’t heard of the Inklings, an authors’ group that met regularly that counted C.S. Lewis and J.R.R. Tolkien as members. Bilbo and the Shire grew with the help of peer feedback.