Up to the turn of the century, Halloween was almost always used with a capital H. While that is still the most common spelling by far, the lowercase variant and Hallow's Eve are gaining prevalence. Other alterations that have actually decreased to today include Hallow e'en, Hallow-e'en, Hallowe'en, and Hallow's eve with a lowercase e. Many people also call it All Hallow's Eve to be ironically archaic, but this is the most accurate spelling of them all. You see, Halloween is a shortening of All-Hallow-even, a Scottish English term describing the evening before All Saint's Day, where mischief was supposed to abound and the witches come out. Sound familiar? This is from a linguistic abomination in Old English, ealra halgena, which also referred to the night in question, but at this point was talking about a pagan holiday that occurred on that very date. So, I guess that since we're all celebrating a pagan holiday, we're paganists?
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd