diabetes

Around 150 CE, Aretaeus of Cappadocia watched patients drink without relief, their bodies seemingly unable to retain water. He named what he saw 'diabētēs,' from the Greek roots for 'through' and 'to go': the body as a siphon, pouring fluid out as fast as it took it in. The word stuck because the image was precise: patients wasted away, their flesh dissolving into urine. Aretaeus wrote in Greek under Roman rule, but his texts circulated in Alexandria's libraries alongside works by Galen and Hippocrates.

Hunayn ibn Ishaq, a Nestorian Christian physician working in Baghdad's House of Wisdom in the 9th century, translated Galen's Greek medical corpus into Arabic. The word 'diabētēs' passed into Arabic as 'diyabīṭas,' preserving the Greek form almost exactly. This fidelity was unusual; many Greek disease names were replaced with Arabic equivalents. Islamic physicians kept the term and added their own observations, distinguishing types by taste and by urine density.

By the 12th century, the medical schools at Salerno and later Paris were teaching from Latin translations of Arabic texts, and 'diabetes' entered the Latin lexicon in essentially its Greek form. Thomas Willis, the English physician who in 1675 added 'mellitus' (honey-sweet) after tasting his patients' urine, was the first to distinguish what we now call Type 1 from a milder insipid form. The word had traveled fifteen centuries and three languages without losing its original metaphor.

The 20th century filled in the biology behind the ancient image. In 1921, Frederick Banting and Charles Best isolated insulin in Toronto, giving diabetics a treatment that had not existed in Aretaeus's time. The siphon metaphor proved durable enough to survive this discovery: the body still passes through glucose it cannot process. Today diabetes affects roughly 10 percent of the world's adult population, and the word that names it is still the Greek of a Cappadocian doctor watching his patients melt.