Answer:
Actually the name Kelsey comes from Chelsea. Chelsea is Mason Musso's ex girlfriend. He was still in love so they wrote a song. He changed the name so it would not be too personal
Keslsy was a girl that Mason Musso liked. Her name was really Chelsea, he wrote a song for her, and Trace Cyrus loved it, but in order for them to make it a song, They had to change the name to Kelsey.