What was the nickname for the African continent at the beginning of the 19th century because of how difficult it was to conquer?

At the beginning of the 19th century, the African continent was often referred to as the "Dark Continent." This nickname reflected the challenges European explorers and colonizers faced in navigating and conquering its vast and largely unexplored interior, as well as the limited knowledge about its diverse cultures and landscapes. The term also carried connotations of mystery and the unknown, reinforcing stereotypes about Africa during that period.