Christopher Columbus has a global holiday and his name forms the basis for states and even nations to this day. Niccolò Machiavelli's last name has become a slanderous adjective. We may have this exactly backwards.
We celebrate the time of year when the veil between this world and other worlds are the thinnist. In the 9th century, the Roman Catholic Church shifted the date of All Saints' Day to 1 November, while 2 November later became All Souls' Day. Over time, it is believed that Samhain, All Saints and All Souls influenced each other, and eventually merged into the modern concept of Halloween.