The term 'Blue Ox' is a reference to the American folktale character Paul Bunyan and his companion, BABE the Blue Ox. Paul Bunyan was a giant lumberjack who was said to have created the Great Lakes with his axe. He was often accompanied by BABE the Blue Ox, a large blue ox that was said to be as tall as a tree. The YAK is a species of wild cattle native to the Himalayas and Central Asia. The ANOA is a species of small wild buffalo found in Indonesia. All of these animals are referenced in the crossword solutions for the term 'Blue Ox'.