Project Moonlark was a project performed by the Black Swan in order to create and genetically modify Sophie. They tweaked her genes, which gave her many advantages, including five special abilities (Telepath, Polygot, Inflictor, Enhancer, Teleporter. Those abilities are known, but there's most likely more) and an impenetrable mind. Afterwards, the Black Swan hid her among humans, which is like how moonlarks send their eggs out to the sea and let the young fend for themselves. The purpose of Project Moonlark is still not entirely clear, but it was probably meant to establish a connection between elves and humans and to have a telepath strong enough to heal broken minds. The project was dubbed Project Moonlark, after Calla suggested it, 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.