There is a name tie in All Hallow’s Eve and Halloween, but that may be all that is left tying the two together. The notion of “Trick or Treat” basically is threatening to pull a trick if no treat is given. This is hardly a saintly idea. Not that I am saying Halloween is always and everywhere bad, but it does not appear to have any authentic tie to All Saints’ Eve anymore. Name and proximity in date are the only ties.
All Saints’ Day (Nov 1st) is immediately followed by All Souls’ Day (Nov 2nd). All Saints’ Day goes all of the way back to the 4th century and was given its current date by Pope Gregory III in the 8th century. For “the holy apostles and of all saints, martyrs and confessors, of all the just made perfect who are at rest throughout the world.” So, we celebrate all of those who have made it into heaven.
All Souls’ Day is a celebration, but it is more so a day for praying for the dead. While All Saints’ Day celebrates those who have made it into heaven, All Souls’ Day is set aside to pray for those in purgatory. They are not yet in heaven, but our prayers can help get them there faster, in a sense. Those in purgatory still have some perfecting to do before going before the Almighty. Praying for the dead on a certain day started in the 7th century and the date was set universally in the 11th century.
Allhallowtide (Hallowtide, Allsaintstide, or Hallowmas season) is the three day observation of these days. It encapsulates All Hallows’ Eve, All Saints’ Day, and All Souls’ Day. The word was first used in 1471, well before any thought of the word Halloween, which dates to about 1745.
Before “trick or treat”, the poor and children would go door-to-door on All Saints’ Day receiving food in return for prayers for the dead on All Souls’ Day. This was called souling.