Who told Swift about the use of children as a source of food?

One proposed source for Swift's satiric essay is John Locke's First Treatise on Government, in which Locke writes of people in ancient societies doing this:

Be it then as Sir Robert says, that Anciently, it was usual for Men to sell and Castrate their Children. Let it be, that they exposed them; Add to it, if you please, for this is still greater Power, that they begat them for their Tables to fat and eat them . . .

In the essay itself, the clueless narrator, who should not be confused with Swift, mentions twice an American acquaintance who has discussed with him how tasty and wholesome a one-year-old child is and how tough the flesh of an older child of about twelve is. While this doesn't offer a specific source for the essay, it plays on exotic tales of cannibalism in the Americas.
While Swift did model his essay on Roman satires, what is striking about it is how original it is: it is in its over-the-top idea of eating children, presented as if it makes logical sense, that the shock value lies. Mostly, the essay arises from Swift's upset over the suffering of the Irish and the unwillingness of their English overlords to make the least sacrifice to alleviate the distressing situation. As the narrator puts it in the essay, saying more than he realizes:

I grant this food will be somewhat dear, and therefore very proper for landlords, who, as they have already devoured most of the parents, seem to have the best title to the children.