I wrote an article a while ago on the link between Celtic and Hindu culture.
This is a subject of interest for many people in the Pagan and Hindu community.
It is believed that in the Iron Ages, the Aryans were an Indo-European tribe that spread East and West. Those who spread West intermingled with the Celts, who spread all the way from central Europe to Ireland.
Most of the Celtic culture in this large swath of land was eradicated or subsumed by The Romans.
However, there was never any Roman conquest of Ireland. So the Vedic/Celtic culture thrived there until the advent of Christianity.
Druidism and the Ancient Religions of India (The Order of Bards Ovates and Druids)
Meet the Brahmins of Ancient Europe (Hindu Wisdom)