With all the theories surrounding Star Wars: The Force Awakens (Snoke's identity comes to mind), is another one that just might hold some merit, which suggests Daisy Ridley's character may have a different name than Rey.
The speculation/theory arises out of the Star Wars: The Force Awakens: Rey's Survival Guide book which is written from the point of view of Rey, in a diary/journal format.
Remember the scene in the movie featuring Rey with the X-Wing pilot's helmet? Well, the Survival Guide reveals information why Rey has it, as well as the name of the pilot -- Dosmit Raeh. We know Rey was dropped off on Jakku at a young age. Is it possible she was abandoned without anyone knowing her name? If she was hidden on Jakku, which some theories suggest, to hide her lineage, she might not even have had a name. We see Rey comes upon the helmet at a young age and makes up stories about the X-Wing pilot. It's possible she might have even taken the pilot's name - Raeh - as her own, "Rey."
Further evidence comes from the novel, Before The Awakening, which states Rey "calls herself Rey."
Of course, this the brings up the question as to who Rey really is: A Skywalker? A Solo? A Kenobi?
Early scripts for Star Wars: The Force Awakens were said to have used the name: Kira Skywalker.
Below you can also check out page revealing how (in part) Rey acquired her skills.