Halloween or All-Hallows-Eve takes place on the night of 31 October in anticipation of All-Hallows-Day (1st November).
Hallow is the old English word for saint.
Halloween is a Scottish variation dating back to the 1700s. The 'een' suffix is a contraction of 'evening'. 'Hallowed evening' or 'holy evening' was later understood to mean eve or 'night before' as with Christmas Eve
Although halloween was imported to the US by British and Irish immigrants, until recently it had a higher profile in America. This is partly because the celebration of Halloween was associated with Catholicism in Britain and Ireland. The more popular commemoration in England was Guy Fawkes Day on November 5, marking the gunpowder plot
All Hallows Day is now called All-Saints-Day in the Catholic calendar. This commemorates Christian martyrs
All Souls Dayfollows on 2 November. On All Souls Day Catholics pray for the 'souls of the (faithful) departed'.