Another thing we would like to call attention to is the earlier presence of Hausa and Central Sudan populations in Saint-Domingue, before the 1770s and 1780s. While most mentions of Gambary and Hausa runaways in the colonial newspaper date from later, there is one early appearance (1766) of a "Gambery" runaway, named la Liberté. The excellent resource, Le marronnage dans le monde atlantique: sources et trajectoires de vie, includes the above ad plus numerous others featuring Hausa and even "Borno" runaways. But what's important to note here is, assuming the Gambary in Saint Domingue were indeed Hausa, which seems likely (the Yoruba term for the Nupe was also used in runaway slave notices as early as 1766, too), then already by 1766, there may have been a small number of peoples from deep in the Nigerian interior or northern Nigeria in the colony.
Indeed, it is possible that before 1766 a few were classified as "unknown" or lumped in with the "Nago" due to the French unfamiliarity with them. The fact that the two groups were called by a Yoruba name for them in 1766 is perhaps indicative of this. This pattern may have been somewhat akin to the way the "Lucumi" label was applied to many Africans in 19th century Cuba who were actually of quite diverse origins. And, considering how close Oyo's relations with the Nupe and Hausa were, it is possible that slaves of northern origins who spent time in Oyo before being sold on the coast were categorized as "Nago" in some cases.
In short, the presence of northerners sold on the Bight of Benin to the French slave traders likely occurred earlier than we realize, probably by the 1720s, when "Malais" Muslim traders visiting the Slave Coast directly appear in European sources. The Nupe, according to sources such as the Kano Chronicle, were said to be supplying firearms to Kano by the 1730s or 1740s. The trade with the coast, which reached Nupe through Oyo, would have linked the Atlantic markets to the savanna and Sahel to the North to at least some degree. Additionally, conflict between Gobir and Zamfara or raids between different Hausa kingdoms may have generated captives that ended up being enslaved and sold to Oyo and beyond. Intriguingly, in 1764, Gobir sacked Zamfara's capital and by 1766, "Gambary" make an appearance in Saint Domingue. Conflict between the Hausa states or with their neighbors inevitably created captives, a small subset of whom appear to have been sold on the Slave Coast by the 1760s.