There has been a mini-flutter among some of my facebook friends who seem to feel for some reason that it is important to write "Hallowe'en" rather than "Halloween".
Halloween has been written without an apostrophe since at least 1773, according to the OED, and among the people using that spelling were Robbie Burns and Queen Victoria. There is no more reason to spell it with an apostrophe than there is to write "fan'cy" (contracted from "fantasy"), "gam'ut" (contracted from "gamma ut"), "lau'nder" (contracted from "lavender"), or "goodb'ye" (contracted from "God be with ye"). I think you can let it go!
For more on why the apostrophe is doomed, visit this post.
For more on the pronunciation of "Halloween", see this post.
P.S. If you find the English language fascinating, you might enjoy regular updates about English usage and word origins from Wordlady. Receive every new post delivered right to your inbox! SUBSCRIPTION IS FREE! You can either:
use the subscribe window at the top of this page
(if you are reading this on a mobile device): send me an email with the subject line SUBSCRIBE at firstname.lastname@example.org