late 14c., "belonging to a beast," c. 1400, "having the qualities of a beast," from Old French bestial (13c.) "relating to animals; beast-like, stupid, foolish, brutal" and directly from Latin bestialis "like a beast," from bestia (see beast). Sense of "below the dignity of a human" in English is from c. 1400, and in many cases does injustice to the beasts. When the beast of the Book of Revelations was meant, the adjectival form bestian (1650s) sometimes was used.
