What's the Origin of Halloween

The current English name Halloween traces back to medieval Christianity. 

The word hallow is derived from the Middle and Old English words for holy

It can also be a noun that means saint. The day before All Hallows' Eve, when an evening mass was celebrated, was known as All Hallows' Eve

At that time, the Christian feast we now know as All Saints' Day was known as All Hallows' Day. Halloween eventually replaced that original three-word term.

considered the earliest known source of elements of our secular Halloween customs, which took place on November 1 but began the previous evening.

The route to October 31—Christian Halloween—is a little more difficult.

Early in the 7th century, Pope Boniface IV established All Saints Day by dedicating the Pantheon in Rome to the saints; however, the date was May 13.