Hanukkah
Approximately 2,200 years ago, there was a war between the Greeks and the Jews.  The Greeks won and forced their culture on the Jews. A group of Jewish people called the Maccabees led by someone named Matityahu revolted against the Greeks and after he died his son Judah Maccabee beat them and liberated Jerusalem. The Maccabees found their Temple defiled. They wanted to rededicate it to God, as the Greeks had been worshipping Zeus there.  As part of the rededication, they needed to relight the menorah, whose source of fuel was olive oil.