Samhain is an ancient Celtic festival , the belief is that the veil between the living is at it's thinest on this day , and that the dead may cross over .

People contact loved ones , whilst trying to avoid bad spirts by dressing up as spirts themselves (confusing them as to who is human and who is a spirit ) . That's were the costumes come from .

It was imported into Amercia from years of Irish immigration .