Sidis develops Vendergood, an artificial language with its own grammar and vocabulary. Details about the language are limited, but it demonstrates Sidis's advanced linguistic abilities and his interest in creating systems and structures.

Vendergood is described as having elements of both Germanic and Romance languages. Its purpose is unclear; it might have been a personal project, a way to explore linguistic principles, or a means of creating a private language.

The creation of Vendergood exemplifies Sidis's intellectual curiosity and his ability to synthesize information from diverse sources. It also suggests a desire to create his own world, independent of external pressures and expectations.