Nollij is a deity in the Spaceman Spiff universe worshipped by the inhabitants of Zark. It appeared only in a single strip. Its worshippers fear the god, evidenced by how they offer sacrifices in order to appease it.
"Nollij" is a play on the word "knowledge". Calvin was in school at the time the fantasy took place, and had been instructed to solve a problem at the blackboard.