Answer: b., for AP style
“Halloween” is derived from “All Hallows Even.” The “een” at the end is a contraction of “even” (meaning evening) which is why the old spelling for Halloween had an apostrophe.
Halloween is the evening before All Hallows, which means “All Saints Day.” “All Hallows” originated in Old English (ealra hālgena) but the first record of “All Hallows Even” is 1556. The day is still sometimes referred to as “All Hallows Eve” and that is sometimes written as Allhallows Eve.
Some Halloween trivia:
All Saint’s Day was first celebrated in 609, in mid-May, but was moved to November 1 by decree of Pope Gregory IV. The day was reserved for prayer for the newly deceased to help them on their passage to Heaven. November 2 was All Souls’ Day.
The ancient roots of All Hallows are in the Pagan feast of Samhain (pronounced sah-win or sow-win), which marked the culmination of the harvest and the transition to the darker days of winter. At Samhain, it was thought that the veil between worlds was at its thinnest, allowing the dead (and other entities, like fairies) to walk among us.
The origin of trick-or-treating was most likely souling, which involved groups of the poor going from door to door on All Souls’ Day requesting soul cakes, spicy, round shortbreads that the more fortunate baked (or, I suppose, being more fortunate, had the servants bake). Both the act of giving them out and the act of eating them were considered forms of prayer for souls in purgatory. Here’s a soul cake recipe. Bake some — a soul is released from purgatory for each one!
Wikipedia provides much more Halloween history.
Michael Fosset offers more tips on AP style on Halloween-related terms.
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