Yes, this would be true. I think a stricter interpretation of Terra Australis Incognita is that it more closely means "The unknown land of the south" but I think we're in 90% agreement. What makes it unique in history and geography is that the land was hypothesized as existing long before it was ever actually discovered, based on nothing more than a concocted global equal weighting theory. Early explorers did a good job mapping the northern hemisphere, and once they learned and all agreed the world was a round ball, they theorized the weight of all the land in the northern hemisphere must be offset or balanced somehow by an equal (but as yet undiscovered and unmapped) amount of land in the southern hemisphere. They assumed that if this wasn't true, then this big ball called earth would be top heavy and flipped around.
