The term 'Mainlanders' Mementos' refers to the traditional Hawaiian leis, which are garlands of flowers or leaves worn around the neck. Leis are a symbol of hospitality and friendship, and are often given as gifts to visitors or exchanged between friends and family members. They are typically made from fragrant flowers such as plumeria, tuberose, and jasmine, and can also be made from shells, feathers, and other materials.