Project Moonlark was a project performed by the Black Swan in order to create and genetically modify Sophie. They played her genes in order to give her several advantages, including five special abilities (Telepath, Polyglot, Inflictor, Enhancer, Teleporter). As a result of this modification she also has an impenetrable mind (almost, Sophie subconsciously lets Fitz in her mind). Afterwards, the Black Swan hid her among humans, similar to how moonlarks send their eggs out to the sea, letting their young fend for themselves. The purpose of Project Moonlark is not yet entirely clear, but it can be assumed it was meant to establish a connection between elves and humans while also having a telepath who was strong enough to heal broken minds. The project was dubbed Project Moonlark by Calla, not because she was tossed out to survive by herself, but because there would always be someone guiding her along - as adult moonlarks do with their young.
In the Enlightened Language, Moonlarks are pronounced "Suldreen." Sophie said this when she was a baby and her parents thought she was trying to say her name. Her father gave her the nickname "Soybean" because that's what they thought she was trying to pronounce. Sophie didn't remember saying Suldreen until Mr. Forkle told her about it later.
Most of Project Moonlark was done at the high seas facility, which has now been abandoned.