Final answer:
Prince Henry the Navigator received his nickname for his sponsorship and promotion of exploration and navigation. He established a navigational school and supported Portuguese mariners in their expeditions.
Step-by-step explanation:
Prince Henry the Navigator received his nickname without actually being a navigator because he sponsored and promoted exploration and navigation. He established a school for navigational studies in Portugal and supported Portuguese mariners in their expeditions. Under his sponsorship, Portugal explored the coast of Africa, discovered new trade routes, and established trading posts up and down the coast of West Africa.