In Roman times, the palm frond was a symbol of victory. When generals won wars, they wore togas decorated with them. When lawyers won cases, their offices were decorated with them. Nike and Victoria, Greek and Roman Goddesses of Victory, respectively, were often represented by palm fronds.
Everybody knows about Palm Sunday, when Christian churches are decorated with palm fronds to commemorate Jesus' triumphant return to Jerusalem. Although I have a hard time deciphering the story, apparently he was triumphant not because he had won a war, but because he had been declared the messiah. When he rode into Jerusalem, people were waving palm fronds.
In ancient Egypt, Hathor was the cow goddess. You have probably seen her depicted with a sun between the cow horns on her head. She was the goddess of life, joy, music, dancing and fertility and her symbol was the palm.
The palm tree has been a sacred symbol for thousands of years. Now it commonly represents a tropical vacation. Maybe that is sacred, too.
The palm below resides near the tropical house at the UC Botanical Garden.