I subscribe to a listserve of Spanish words and their etymology (I am a translator) and today's word was Halloween. (Yes, Halloween is called Halloween in Spanish. B/c it's not a holiday they celebrate. Till recently) And the reason Halloween is so popular in the US and Great Britain/Ireland/Scotland is because the traditions come from an old Celtic festival, and it was brought to the US by Irish immigrants. So that's how we got it but so many other countries didn't. Neat!