From the experts:
One of the many faux-Medieval names invented by George R.R. Martin for his A Song of Ice and Fire series of books, the source of HBO's Game of Thrones. Princess Myrcella Baratheon is the daughter of Cersei Lannister and (secretly) her brother Jaime. Their younger brother Tyrion sends her to Dorne to be married to the Dornish prince Trystane Martell to seal an alliance between the two houses.