It is a beautiful title. One of my favorites in fact.
The biblical and foundation of the title (Mary, Star of the Sea)is based on 1 Kings 18:41-45. This text refers to a little cloud appearing above the sea as a sign of hope implying that rain will come and free the land from drought. The little cloud (small as a man’s hand) seen from Mt. Carmel is believed to be the “Star of the Sea” and Mary, represents, the sign of hope which announces freedom and renewal. The Carmelites built a church on Mt. Carmel and gave it the title “Stella Maris.”
St. Jerome is commonly attributed to have refered to Mary using the expression “Stella maris.”