Interesting. In fact, I recently discover Halloween means "All Hallows Eve" which is the day before "All Saints Day". All Saints day is a day used to honour all saints known and unknown in the world. Its pretty interesting how one day could even be called "the devil's birthday" (which it's not) to some lead up to an innocent Christian holiday no one hardly knows in modern society. I bet the book would answer a lot of questions about Halloween origin. Thank you.
This is an indirect and not so quick answer to your question, but you might enjoy the book "Halloween: An American Holiday, An American History." https://amzn.com/1565543467
Of course there are witchy and Wiccan-type books catered to Halloween, not so much anything written specifically for spirit-keepers though. And you can't be sure if any of the witchy books have correct info. It never hurts to read some scholarly background resources when looking for ideas.
Well, it depends on how much of a stickler you are for history or not. ;P
But yeah wouldn't it be great to have an actual Halloween magick manual geared towards spirit-keepers?
Yes, the book would help explain it but you can probably find it on the internet as well.
Halloween as we know it is pretty much an America holiday, grown over the years from many traditions (Celtic, Roman, British, Scots, Irish, American, etc.).
The word is indeed a truncated form of All Hallows Evening, which became shortened to E'en. That's what the Christians called it. November 1 is All Saints Day, and November 2 is All Souls Day.
Theses dates coincide with the Mexican (and later Spanish-Catholic) Dia de Muertos, the Day of the Dead. Hence you start to see more of the Spanish cultural decorations in stores now alongside the pumpkins and candy.
October 31 was called Samhain ('sow-en'), summer's end, by the Celts, and celebrated as a harvest festival.