Trick or treat! Happy Halloween, guys! ^^
Found this very useful info in Wikipedia regarding Halloween:
The term Halloween is shortened from All Hallows' Even (both "even" and "eve" are abbreviations of "evening", but "Halloween" gets its "n" from "even") as it is the eve of "All Hallows' Day", which is now also known as All Saints' Day.
The name jack-o'-lantern can be traced back to the Irish legend of Stingy Jack, a greedy, gambling, hard-drinking old farmer. He tricked the devil into climbing a tree and trapped him by carving a cross into the tree trunk. In revenge, the devil placed a curse on Jack, condemning him to forever wander the earth at night with the only light he had: a candle inside of a hollowed turnip. The carving of pumpkins is associated with Halloween in North America, where pumpkins were readily available and much larger, making them easier to carve than turnips.
Honestly, I think "Happy Halloween" is ironic. How can you be happy when it means that evil spirits are prowling on your backyard? ^^