In old Celtic traditions all Hallows Eve was known as Samhain, a fire festival marking the end of harvest season. hearth fires were relit from communal celebration bonfires. As this marked a period of transition into winter it was held a time when the " veil" between the worlds of the living and dead might allow ancestors to cross over. Dressing in costume was held to prevent kidnapping by spirits as were the food offerings left out, although the 3 day celebration was in reality about other kinds of spirits and feasting. The early christian church appropriated the existing pagan party to venerate deceased Saints and the intermixing of traditions arrived in the US in the19th century via primarily Irish immigrants. All Hallows Eve was contracted to Halloween along the way while costumes and food continued in milder forms as Trick Or Treat.
So it goes.
Wishing all a festive Samhain, Halloween and a good day in general.