All Hallow's eve is believed to be in reference to the eve before honoring the dead (which Jairica will share about November 1st). There are many other names by which people have referred to October 31 throughout history.
-Hallowe'en or now Halloween a contraction for "All Hallow's Evening"
-All Saint's Eve
As with many holidays, there are traditions and staples that evolve over time that are far different and detached from the original meaning and purpose of the holiday. For example, Trick-or-Treating: Our purpose for trick-or-treating now is to either give candy or try and trick someone by scaring them (or some other minor prank). Originally, the purpose was the poor going door to door for food in exchange for prayers for the dead on All Saint's Day (November 1 evening-November 2).
We of course are left with other common aspects of Halloween such as costumes, pumpkins, scary movies, haunted houses, ghost stories at bonfires, fear of cemeteries and the woods, fears of black cats, and so many more!