All data was taken from the english Wikipedia
A palm branch (or palm frond or palm stem), usually refers to the leaves of the Arecaceae (sometimes known by the names Palmae).
The palm branch was a symbol of triumph and victory in pre-Christian times. The Romans rewarded champions of the games and celebrated military successes with palm branches. The motto of the HMS Nelson and the University of Southern California is “Palmam qui meruit ferat”, which means in Latin, “Let him bear the palm who has deserved it”. Jews followed a similar tradition of carrying palm branches during festive times.
Early Christians used the palm branch to symbolize the victory of the faithful over enemies of the soul, as in the Palm Sunday festival celebrating the triumphal entry of Jesus into Jerusalem. In Christian art, martyrs were usually shown holding a palm frond, representing the victory of spirit over flesh, and it was widely believed that a picture of a palm on a tomb meant that a martyr was buried there.
Origen calls the palm (In Joan., XXXI) the symbol of victory in that war waged by the spirit against the flesh. In this sense it was especially applicable to martyrs, the victors par excellence over the spiritual foes of mankind; hence the frequent occurrence in the Acts of the martyrs of such expressions as “he received the palm of martyrdom.” On 10 April 1688 it was decided by the Congregation of Rites that the palm when found depicted on catacomb tombs was to be regarded as a proof that a martyr had been interred there. Subsequently this opinion was acknowledged by Mabillon, Muratori, Benedict XIV and others to be untenable; further investigation showed that the palm was represented not only on tombs of the post-persecution era, but even on pagan tombs.
The general significance of the palm on early Christian monuments is slightly modified according to its association with other symbols (e.g., with the monogram of Christ, the Ichthus (Fish), or the Good Shepherd). On some later monuments the palm was represented merely as an ornament separating two scenes. Palms also represented heaven, evidenced by ancient art often depicting Jesus in heaven among palms.
In Judaism, the date palm represents peace and plenty, and is one of the Four Species (Lulav) used in the daily prayers on the feast of Sukkot. It is bound together with the hadass (myrtle), and aravah (willow) The palm may also symbolize the Tree of Life in Kabbalah.
Muhammad is said to have built his home out of palm, and the palm symbolizes rest and hospitality in many cultures of the Middle East. The first muezzin climbed palm trees to call the faithful to prayer, from which the minaret developed.
The sacred tree in Assyrian mythology is a palm that symbolizes Ishtar connecting heaven, the crown of the tree, and earth, the base of the trunk. Palm stems represented long life to the Ancient Egyptians, and the god Huh was often shown holding a palm stem in one or both hands. The palm tree was a sacred sign of Apollo in Ancient Greece because he had been born under one in Delos. In ancient Mesopotamia, the date palm may have represented fertility in humans. The Mesopotamian goddess Inanna, who had a part in the sacred marriage ritual, considered herself the one who made the dates abundant.
In some cultures they get it from a church and make crosses out of them and use it as a symbol as god.