The word "revenant" is derived from the Latin word, reveniens, "returning", or the French word "revenir" meaning "to come back". Revenants share a number of characteristics with folkloric vampires.
A revenant is a ghost visible to the common eye, or an animated corpse that has returned from the grave. While this is very close to the zombie and vampire, there are differences that make it distinctive from the two.
Like the African folklore zombie, a revenant usually returns for a specific purpose, only not under the command of a “master”. History has logged many accounts of mortals crossing paths with revenants. In most cases, they are documented to have been harassing friends and family, or in some cases, even carrying out acts revenge against their killers.
In reality, the origins of these creatures derived from people coming in contact with bodies after their burial, for whatever reason, and not understanding the stages of decomposition and the effects it had on the body. From appearances people assumed the deceased bodies looked too life-like and hence must be getting out of their graves and having a "life". And what kind of life could such creatures have but something vile? Hence stories evolved to explain this presumed activity. As time went on the stories grew and adapted, until the legends of the undead became common.
From these beliefs, came the need to rid themselves of such creatures before they became a problem. The logical choice was to incorporate the traditions used at the time of All Hallows (or Halloween for America). This time was used to prepare for the new year that began on November 1st. A celebration of varied activities was conducted to plan for and divine the future, remember those who had died (which included in many places, opening tombs to allow spirits to pass on to the next life), and to prepare for the harsh, cold and boring winter to come by having one last "fun fling".
It was natural for the revenants to be included or connected with the activities because, hopefully, these celebrations would appease any roaming spirits, showing them that they had not been forgotten or abandoned, and to direct them toward the afterlife, thereby helping both the celebrants (by ridding themselves of the revenants) and the undead (by showing them the way to a better place).
Among the activities commonly associated with the period celebrations were divination (by tarot, runes and other folklore methods), remembrance (by dressing up as saints or deceased family members), protection (by dressing differently as a type of revenant, by wearing garb of the opposite sex or by wearing one's own clothes inside-out so the seams showed) and most importantly entertainment (by stories, games, contests and music).