Why did the French call their Mauritanian colony Le Grand Vide?

The French referred to their colony of Mauritania as Le Grand Vide (the great void) because, as long as the local population remained quiet, there was very little evidence of a French presence in the territory.1

This nickname reflected the colonial administration's limited exertion of control over the region, particularly outside of the southern areas, throughout much of the early 20th century. While France maintained a colonial administration, the vast, sparsely populated desert landscape meant that the French footprint was often minimal, leading to the characterization of the colony as a "great void".1