In The Force Awakens Rey's X-wing pilot helmet is salvage from the wreckage that litters Jakku. The writing on the side translates to Ræh, a former Rebel pilot. This most likely means that Rey isn’t her birth name and she just took it from the helmet.

CobaltLeopard47 on December 9th, 2018 at 18:11 UTC »

This is actually a game changer for me now I know why she only has one name

Batbuckleyourpants on December 9th, 2018 at 18:39 UTC »

Dosmit Ræh served as a captain in the Alliance to Restore the Republic, a rebel group that opposed the reign of Sheev Palpatine's Galactic Empire. A member of the Rebel Alliance Starfighter Corps, she flew a T-65B X-wing starfighter. Prior to the outbreak of the Galactic Civil War, she served with the Tierfon Yellow Aces, a Rebel starfighter squadron.[2] Several years after the war, Ræh's flight helmet was recovered by a young desert scavenger on Jakku named Rey.

When Rey was a girl, Ræh became an important figure in Rey's life, with the young scavenger dreaming up stories about what Ræh was like and where she might have come from. Rey created a fighter pilot doll using a flight suit she recovered from a cargo container, and she would often wear Ræh's flight helmet. Together, Rey and "Ræh" would go on adventures by exploring Rey's home, the downed All Terrain Armored Transport called Hellhound Two, as well as the sands outside of the AT-AT. Rey eventually grew out of playing with the doll, but she kept the memory of Dosmit Ræh alive by keeping the doll and her helmet in her possession throughout her years on Jakku

grounded_astronaut on December 9th, 2018 at 18:40 UTC »

So does this mean child-Rey pulled this off of a skeleton? Ræh's body was presumably still there.

Her true birth name is Aegon Targaryen.