Original: Europa was discovered in 1610 by Galileo Galilei (and possibly independently by Simon Marius), and named after a mythical Phoenician noblewoman, Europa, who was courted by Zeus and became the queen of Crete.
Simplified: Galileo Galilei first saw the moon in January 1610 (he did not know Marius had found it). Simon Marius was the one who had the idea of the name 'Europa.'