Wikipedia
The Álfablót or the Elven sacrifice was a pagan Scandinavian sacrifice to the elves towards the end of autumn, when the crops had been harvested and the animals were most fat. Unlike the great blóts at Uppsala and Mære, the álfablót was a local celebration at the homesteads and they were mainly administered by the lady of the household. Nothing is known about the particular rites because they were surrounded by secrecy and strangers were not welcome to the homesteads during the celebrations. However, since the elves were collective powers with a close connection to ancestors and fertility, it is possible that the álfablót concerned ancestor worship and the life force of the family. It also appears that Odin was implied and that the master of the household was called Ölvir when administering the rites. The first element of Ölvir means "beer", which was an important element in Norse pagan sacrifices generally.
There is a notable account of the ceremony in Austrfararvísur by the Norwegian skald Sigvatr Þórðarson, where he tried to impose on the privacy of a series of homes during the sacred family holiday, a privacy that he was accordingly asked to respect.