Halloween comes from which druid holiday?

Samhain, which is pronounced sow-en because Irish phonetics do not get along with English ones. It was the Celtic New Year, but also similar to the Mexican day of the dead. It didn't start until evening, because the Celts considered sunset to be the start of the day, so it was the night of October 31 and the day of November 1. It became All Hallow's Evening under the Christians, Hallows meaning spirits; this eventually was shortened to Halloween.