Like Greeks and Romans, barbarians worshipped hundreds of gods and goddesses with specialized functions. They regarded certain mountains, lakes, rivers, or groves of trees as sacred because these were linked to deities. Rituals to honor the gods were held outdoors rather than in temples or churches, often at certain points in the yearly agricultural cycle. Presided over by a priest or priestess understood to have special abilities to call on the gods’ powers, rituals sometimes involved animal (and perhaps human) sacrifice. Among the Celts, religious leaders called druids (DROO-ihds) had legal and educational as well as religious functions, orally passing down laws and traditions from generation to generation. Bards singing poems and ballads also passed down myths and stories of heroes and gods, which were written down much later.

The first written records of barbarian religion came from Greeks and Romans who encountered barbarians or spoke with those who had. They understood barbarian traditions through their own belief systems, often equating barbarian gods with Greco-Roman ones and adapting stories and rituals to blend the two. This assimilation appears to have gone both ways, at least judging by the names of the days of the week. In the Roman Empire the days took their names from Roman deities or astronomical bodies, and in the Germanic languages of central and northern Europe the days acquired the names of corresponding barbarian gods. Jupiter’s day, for example, became Thor’s day (Thursday); both of these powerful gods were associated with thunder.