In the past, the Dayak were feared for their ancient tradition of headhunting practices (the ritual is also known as Ngayau by the Dayaks) . Among the Iban Dayaks, the origin of headhunting was believed to be meeting one of the mourning rules given by a spirit which is as follows:
The sacred jar is not to be opened except by a warrior who has managed to obtain a head, or by a man who can present a human head, which he obtained in a fight; or by a man who has returned from a sojourn in enemy country.