Zealot in Hebrew is kanahi, but the word is Greek. The term initially was meant to describe a certain sect of Jewish people in the first century CE that had political power and attempted to overthrow control of their people by the Romans. This was especially important in regard to control of Israel, since this was considered to be the seat of Jewish power and their rightful heritage, as passed down by King David.
The zealot in the oldest sense applied to many people, who were considered a sect of Judaism. They were first led in the Common Era by Judas of Galilee, who held to the idea that Roman rule was incompatible with Jewish freedom, and that the Jews should be free of Roman control. This culminated, eventually in an actual revolt, the Great Jewish Revolt. Zealots, especially those in the Iudaea Province, captured Jerusalem and were able to hold it until 70 CE. Rome eventually retook Jerusalem, leading to the destruction of the Second Temple.
It can’t be questioned that the zealots used violence in an attempt to gain freedom. Violent acts were met with violent acts by Rome, and further oppression of the Jews. Still, remnants of these ideas exist, and many see a specific zealot group, the sicarii as the first religious terrorists. The sicarii were trained assassins, meant to spread fear and discord among the Romans, in the hopes that they would gain control of Israel and their freedom.
There are specific indications in the Mishnah that the activities of the zealot were not approved, and that zealots were likely damned. The Talmud also refers to a zealot as “wild,” and speaks against their aggressive acts. Zealots advocated killing Jews who went along with Rome’s policies, which won them great criticism among the other sects of Judaism.
Today, the term zealot is applied often to people so overcome with religious fervor that they act in ways harmful to others. Having religious zeal is not a bad thing, but when it is combined with actions that hurt others, it is zealotry at its worst. The zealots of the first century were not long thinking in their actions and, overcome by their beliefs, they acted in ways that did not best serve their Jewish community and resulted in significant anti-Jewish sentiment and tougher laws for all Jews. Their cry for freedom was muted by their acts of terrorism.