The word “hallowed” means made holy or consecrated. There is nothing hallowed in the celebration of Halloween.
Like some other holidays that originated in paganism but are celebrated by “Christian” churches today—albeit with new names—Halloween also marched right out of pagan religious practices and into mainstream religion. New labels were applied to centuries-old trappings, traditions, and celebrations from the pagan world, and these practices continued to be observed on or around the same time of the year.