Passion Flower or passion vines is a common name for a genius of about 500 different flowering perennial plants, called passiflora. The plant is native to North and south America. When Spanish explorers first saw passion flower they associated it with Christ, to the Spanish the many fringes represented the crown of thorns wore by Christ. This association lead to the name passion flower.
Passion flower was grown as a semi-domesticated crop by the Aztecs and Incas for thousands of years for its fruit. Use of passion flower as a calming herb and sleep aid spread throughout Europe and that use persists to this day.