Did you know...What name 'Halloween' means...

The word Halloween is a shortened word for "All Hallows' Even," which is the eve of All Hallows' Day which is another name for All Saints' Day, the day Catholics commemorate all the saints.

So there you go, next time you want to trick your friends instead of saying Happy Halloween, just say Happy All Saint's Day!

Source: http://people.howstuffworks.com/culture-traditions/holidays/halloween1.htm