There were very strong similarities between the early religious rituals of the Hindu Brahmin and the Old Irish Druids. This article is about new Irish Kings bathing with a sacrificed horse and compares it with the traditional Vedic Hindu royal inauguration. And there are other similarities between ancient Indic and Irish religions; as well as relationships to Greek, Roman and Norse religions.
This connection seems odd — Ireland is a long distance from India; the Irish and Indic languages separated about 5500 years ago; the two populations have different Y-chromosome haplogroups. I think these religious parallels may suggest the great dominance of the early Indo-European culture.