Samhain is mentioned in some of the earliest Irish literature. Many important events in Irish mythology happen or begin on Samhain. It was the time when cattle were brought back down from the summer pastures and when livestock were slaughtered for the winter. In much of the Gaelic world, bonfires were lit and there were rituals involving them, as at Beltane. People and their livestock would often walk between two bonfires as a cleansing ritual, and the bones of slaughtered livestock were cast into its flames. Samhain (like Beltane) was seen as a time when the "door" to the Otherworld opened enough for the souls of the dead, and other beings, to come into our world. Feasts were had, at which the souls of dead kin were beckoned to attend and a place set at the table for them. It has thus been likened to a festival of the dead. People also took steps to protect themselves from harmful spirits, which is thought to have led to the custom of guising.
Begging at the door grew from an ancient English custom of knocking at doors to beg for a "soul cake" in return for which the beggars promised to pray for the dead of the household. Soul cakes, a form of shortbread — and sometimes quite fancy, with currants for eyes — became more important for the beggars than prayers for the dead, it is said.
The refrains sung at the door varied from "a soul cake, a soul cake, have mercy on all Christian souls for a soul cake," to the later:
Soul, soul, an apple or two,
If you haven't an apple, a pear will do,
One for Peter, two for Paul,
Three for him who made us all.
Soul cake, soul cake, please good missus, a soul cake.
An apple, a pear, a plum, or a cherry, any good thing to make us all merry.
Christanity may have bastardized the Celtic Samhain, but at least it still had meaning... whereas the secular America has reduced All Hallows' Eve to an orgy of sensory gratification, and the hypersexualization of females.
As a child, I simply associated this night with receiving candy from strangers... keep to the more affluent "safe" neighborhoods and covet the brand name candies... because of course, high fructose corn syrup and petroleum-based colorants = good, and it's so much easier to conceal a razor blade in an apple than tamper with a Snickers bar?