Literature from some of these museums, together with any number of website postings, will inform the inquisitive that the device was used to torture transgressors during the Middle Ages. Some sources claim it to be a tool of the Inquisition. The various ‘pears’ consists of three or four metal lobes connected at one end by a hinge. In the earliest examples, a spring-loaded internal mechanism forces the lobes apart and a retraction of the lobes is only possible by the manipulation of the spring by means of a secondary pin. Other versions lack the spring and can only be opened or closed by means of a screw, often elaborate in its decoration.

It has been proposed that, by inserting the device into different orifices and then gradually expanding it, medieval torturers could punish the wicked according to their crime. Thus the ‘pear’, it is imagined, was forced into the mouth of a blasphemer; the vagina of a woman deemed guilty of witchcraft, adultery, prostitution or of inducing a miscarriage; or the anus of a homosexual man[.]

Any historian looking at such an object and reading these descriptions would remain skeptical, of course.

• Charles Bishop, "The “pear of anguish”: Truth, torture and dark medievalism." (2014) International Journal of Cultural Studies, 17(6), 591–602.

There are no medieval accounts of any torture device resembling the "pear of anguish" (choke pear, pope's pear, etc.), and no existing models from the medieval period. The earliest models described are too elaborate and limited in function to have served as gags or instruments of torture, the later examples bear the hallmarks of fakes and reproduction, as with the Iron Maiden and similar "medieval torture devices" which filled the European and American imagination in the 18th through early 20th centuries. There is no evidence of their use as actual torture devices, either during the middle ages or during the period of slavery in America.

Just to be clear: African-American slaves were absolutely subject to torture. Likewise, the idea of their status as slaves and their torture elicited sexual narratives of a sadomasochistic nature.

Krafft-Ebing formally introduced the terms "sadism" and "masochism" into the psychopathological lexicon, labeling them "the fundamental forms of psychosexual perversion, which may make their appearance at any point in the domain of sexual aberration." In dozens of case studies, he documented his subjects' fantasies and ritual enactments of pain scenarios that replicated those of humanitarian reform: scenes of judicial torture (by bastinado and knout), schoolboy floggings, the slaughter and abuse of domestic animals, the physical abuse of mental patients ("brutal, uneducated female warders beating me mercilessly"), and the flagellation of slaves. One of Krafft-Ebing's subjects confessed that his first experience of sexual excitement at puberty was prompted by reading Uncle Tom's Cabin; a generation later, Sigmund Freud reported that Stowe's novel was cited by many of his patients (whom he labeled hysterics and obsessional neurotics) as the original stimulus for their common fantasy that "a child is being beaten."

• Karen Halthuten, "Humanitarianism and the Pornography of Pain in Anglo-American Culture" (1995), The American Historical Review

So what you have is a confluence of interest in medieval torture and a rising awareness of the sexual implications of corporal punishment around the 18th to 20th centuries, which in the United States included a strong segment of interest in the sexualization of American slavery.

Even with that in mind, I have not found any narrative which specifically listed the "pear" as an instrument of slave torture. The closest I could find were accounts of the speculum oris, which was a device like a pair of pliars with a thumbscrew, inserted into the mouth to force the jaw open. Lydia Maria Child describes this and other devices in An Appeal in Favor of That Class of Americans Called Africans (1833).