My M.A. thesis, completed in 1997 at the University of Colorado in Boulder under the guidance of Fred Denny, Ira Chernus, and Robert Lester, advances a peculiar and, no doubt, very naive idea about how the early Muslim community came to be known as “believers:” in accordance with its pre-Islamic usage, the term initially meant “those who give protection” to the Prophet Muhammad, but came to mean “believers” as the community’s self-definition evolved. This is not an idea I would feel qualified either to defend or refute today, but it has found some sympathetic ears among scholars and may still be of interest.
David Reeves Vishanoff. “On the Origin and Development of the Qurʾānic Use of Āmana.” M.A. Thesis, University of Colorado, 1997.
Here is a scanned pdf of the thesis.