The word pill ultimately comes from the Latin pila “ball,” or more specifically from the Medieval Latin pilula “little ball.” So a pill is a small ball or pellet of medicine. This is the earliest sense of the word in English, dating to before 1400, appearing in the English translation of Lanfranc’s Science of Cirurgie in Bodleian Ashmole MS 1396:
He schal ofte be purgid wiþ pillis cochie rasis.
(I’m not sure exactly what “cochie rasis” is. It is some kind of medieval purgative. And the “1396” is just the manuscript number, not a year.)
How pill came into English is unknown. It could be a direct lift from Latin, or it may have come via French or other European language.
Several slang senses have developed out of it:
The Pill is an oral contraceptive, a sense that appears by 1956.
Pill is used also to describe various types of small, round objects, a sense that goes back to around 1450. More specifically, these senses have included testicles (1608); bullets, cannonballs, or other types of ammunition (1618); and a ball used in a sport or game (1896), originally billiard balls but later other types, and especially in the U. S. a basketball.
The medicinal association gave rise to the slang sense of something unpleasant but necessary, as in a bitter pill to swallow. This sense dates back to at least 1548 when Nicholas Udall translating Erasmus’s commentary on the New Testament wrote
Yet cannot they abide to swallowe down the holsome pille of the veritie beeyng bittur in their mouthes.
By 1830, this sense had morphed into that of an unpleasant person. From William Carleton’s Traits and Stories of Irish Peasantry of that year:
“I tell you,” observed O’Neil, “there’s a bad pill* somewhere about us.” [...] *This means a treacherous person who cannot be depended on.
“pill, n.3,” Oxford English Dictionary Online. Third edition. March 2006. Web. 9 October 2011.
“pill, n.,” Green’s Dictionary of Slang. 2011. Web. 9 October 2011
Copyright 1997-2014, by David Wilton