Zabu was born in the Savage Land. While still a cub, his mother and siblings were killed by human hunters. He wandered the Savage Land on his own, teaching himself how to survive as he grew to adulthood. Zabu encountered a young boy named Kevin Plunder as he was about to be attacked by a group of human Savage Land natives. Zabu saved Kevin, and the two became companions. Zabu protected the boy as he grew to adulthood, and eventually took on the name Ka-Zar, which means "son of the tiger." Zabu was brought to near-human intelligence due to exposure to radioactive mists.