In general, an offering is something given to someone else. Offerings for the deities, spirits, and other Gaelic entities is something that survived into modern day from the Fairy Faith. The custom is to not consume any edible offerings.
There are two schools of thought as to why Gaelic cultures did not consume their offerings. The first is that the essence of the offering is taken by the non-corporeal entities, and what is left is essentially rotten or no-good. The second is that it’s bad hospitality to offer something then take it away from a guest.
Since the offering isn’t eaten, it’s suggested that instead it be buried, thrown into a moving stream, or thrown into a fire. Those options may not be available to everyone, so leaving something in a tree or bush is another way I’ve seen Gaelic Polytheists leave offerings. If none of that is doable, respectfully throwing away the offering when enough time has passed is also acceptable.
But why make an offering? There are many opinions as to why, and it can depend on the relationship.
First reason is relating to hospitality. Having guests over means providing food and drink, and this is thought to extent to non-corporeal guests as well. This is the reason for most of my offerings, as I see it as hospitable if I am inviting a deity or other entity into my home that I at least provide them with some water. Likewise, if I visit a place I leave offerings as a guest bringing a hostess gift to a party might.
The second reason relates to mythology, wherein the Sons of Mil or Milesians — the last invasion and thought to be the Gaels — drove the Tuatha Dé Danann underground into the hills. After the Tuatha deprived the Milesians of crop to feed them, they made a treaty that the Milesians would give offerings to the Tuatha in order for the Tuatha to leave them alone.
A third reason may be because of a relationship one has with an non-corporeal entity, wherein there’s an agreed upon arrangement to make offerings to the entity.
Another reason is to give thanks or because one simply likes the entity. It’s a way to show appreciation and gratitude.
- “Offerings for Celtic Deities and the Good Folk” by Aithne
- On Offerings to Manannán mac Lír by Eddie Marsson