The Celtic tradition of headhunting was centred around the belief that the head housed a person's soul. Ancient Romans and Greeks recorded the Celts' habits of nailing embalmed heads of personal enemies to walls or dangling them from the necks of horses. Heads were also offered as sacrifices to the gods.
The Headhunter unit itself is fictitious, and is largely based on popular legends about Celtic warrior women. One such tale does tell of a Celtic queen who beheaded the Roman centurion who fully had his way with her, and presented the head to her husband as a sign of her continued faithfulness.