The Israeli term for New Year's night celebrations, "Sylvester," was the name of the "Saint" and Roman Pope who reigned during the Council of Nicaea (325 C.E.). The year before the Council of Nicaea convened, Sylvester convinced Constantine to prohibit Jews from living in Jerusalem. At the Council of Nicaea, Sylvester arranged for the passage of a host of viciously anti-Semitic legislation. All Catholic "Saints" are awarded a day on which Christians celebrate and pay tribute to that Saint's memory. December 31 is Saint Sylvester Day - hence celebrations on the night of December 31 are dedicated to Sylvester's memory.But why do Israelis use the term? Hanan Cohen is quoted here:
It's just because Israel is a Jewish state. The [Jewish] new year holiday is celebrated on the eve of Tishrei 1st. People who immigrated to Israel from western countries still wanted to celebrate the "old" new year, like at home, but could not say that they were celebrating the new year so they used instead the Catholic name of the day, Sylvester. That's why the Jews in Israel celebrate the event using a name of a Catholic saint.
But what is the origin of the name "Sylvester"? It's related to a Latin word, silva, which means "wood, forest". That word makes up the "-sylvania" in Pennsylvania ("Penn's forest") and Transylvania ("beyond the forest"). In addition to the name Sylvester, we also get the names Sylvia and Silvan - as in the former Israeli foreign minister Silvan Shalom.