Kakko of Friuli

Kakko (also Cacco or Gacco) (died 617) was the joint duke of Friuli with his elder brother Tasso from their father's death (611) to their own. Their father was Gisulf II. In or around 611, Gisulf was killed fending off an Avar invasion.

Kakko and Tasso, along with their brothers Radoald and Grimoald, escaped the Avars and evaded capture, successfully setting themselves up as Gisulf's successors. During their reign, they ruled over the Slavs of the valley of the Gail up to Matrei and imposed a tribute upon them. Tasso and Kakko were treacherously killed one day by Gregory, exarch of Ravenna. The exarch, having invited Tasso to Oderzo for a ceremonial beard-cutting, had him and his brother hunted down and killed. Radoald and Grimoald fled to Arechis I of Benevento and Friuli passed to their uncle Grasulf II.

...
Wikipedia