The word holiday comes from the Old English word hāligdæg (hālig “holy” + dæg “day”). The word originally referred only to special religious days. Today it means any special day of rest or relaxation, as opposed to normal days away from work or school.
In Sweden, we just finished the Midsummer celebrations, and in the Northern hemisphere most people are looking forward to a smaller summer break, also called summer holidays. At least in the Commonwealth nations, while the US may just call it a vacation – although today is a holiday. Happy 4th July !).