Palm Sunday, the Sunday before Easter, is so called from its being commemorative of Christ's triumphal entry into Jerusalem; it is observed by the Greek and Roman Churches; in the latter palm branches are blessed by the priest before mass, carried in procession, distributed to the congregation, carried home by them, and kept throughout the year.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Palm, Johann Philipp * Palma