At the end of life, Keeley says, the majority of interactions will be nonverbal as the body shuts down and the person lacks the physical strength, and often even the lung capacity, for long utterances. “People will whisper, and they’ll be brief, single words—that’s all they have energy for,” Keeley said. Medications limit communication. So does dry mouth and lack of dentures. She also noted that family members often take advantage of a patient’s comatose state to speak their piece, when the dying person cannot interrupt or object.

Read more: What good is thinking about death?

Many people die in such silence, particularly if they have advanced dementia or Alzheimer’s that robbed them of language years earlier. For those who do speak, it seems their vernacular is often banal. From a doctor I heard that people often say, “Oh fuck, oh fuck.” Often it’s the names of wives, husbands, children. “A nurse from the hospice told me that the last words of dying men often resembled each other,” wrote Hajo Schumacher in a September essay in Der Spiegel. “Almost everyone is calling for ‘Mommy’ or ‘Mama’ with the last breath.”

It’s still the interactions that fascinate me, partly because their subtle interpersonal textures are lost when they’re written down. A linguist friend of mine, sitting with his dying grandmother, spoke her name. Her eyes opened, she looked at him, and died. What that plain description omits is how he paused when he described the sequence to me, and how his eyes quivered.

But there are no descriptions of the basics of last words or last interactions in the scientific literature. The most linguistic detail exists about delirium, which involves a loss of consciousness, the inability to find words, restlessness, and a withdrawal from social interaction. Delirium strikes people of all ages after surgery and is also common at the end of life, a frequent sign of dehydration and over-sedation. Delirium is so frequent then, wrote the New Zealand psychiatrist Sandy McLeod, that “it may even be regarded as exceptional for patients to remain mentally clear throughout the final stages of malignant illness.” About half of people who recover from postoperative delirium recall the disorienting, fearful experience. In a Swedish study, one patient recalled that “I certainly was somewhat tired after the operation and everything … and I did not know where I was. I thought it became like misty, in some way … the outlines were sort of fuzzy.” How many people are in a similar state as they approach death? We can only guess.

We have a rich picture of the beginnings of language, thanks to decades of scientific research with children, infants, and even babies in the womb. But if you wanted to know how language ends in the dying, there’s next to nothing to look up, only firsthand knowledge gained painfully.

After her father died, Lisa Smartt was left with endless questions about what she had heard him say, and she approached graduate schools, proposing to study last words academically. After being rebuffed, she began interviewing family members and medical staff on her own. That led her to collaborate with Raymond Moody Jr., the Virginia-born psychiatrist best known for his work on “near-death experiences” in a 1975 best-selling book, Life After Life. He has long been interested in what he calls “peri-mortal nonsense” and helped Smartt with the work that became Words on the Threshold, based on her father’s utterances as well as ones she’d collected via a website she called the Final Words Project.