Public holidays in the ancient world were both religious and national in character. The attendant rites which accompanied pagan idolatry, including animal sacrifice, were integral to the celebrations. This practice had come down from the original corruption of religion at Babel.
“Nimrod, being the founder of both their civilization and their religion, served as king, and chief priest. The later kings of Sumer (as Shinar is known today) followed his example in this, as in all else.”
Christine Miller, The Story of the Ancient World, p. 40.
“The ritual alone which accompanied divination practices and incantation formulae was a chief factor in the celebration of festival days …”
“Babylonian and Assyrian Religion,” The Encyclopaedia Britannica, Vol. 3, p. 115.