Several details of Pope Francis’s coat of arms pay homage to his Jesuit roots. The sunburst symbol of the Society of Jesus is prominently displayed on the blue shield. The sunburst also signifies Jesus. Beneath it, the star signifies Mary and the spikenard flower honors St. Joseph.
The Latin motto beneath the shield–“Miserando alque eligendo”–means “Having mercy, he called him.” It is a reference to the account of Jesus calling the tax collector Matthew. The motto refers to the call the pope felt to enter the Jesuits, which occurred on the feast of St. Matthew when Jorge Bergoglio was 17 years old.
UPDATE: For more on this, see “Is the Pope Still a Jesuit?” from America magazine.