The Polychronicon is a book written by Ranulf Higden around 1342 or so. Higden was a monk in a monastery in Chester, England, and thanks to that book, he’s pretty famous as a medieval historian. The Polychronicon isn’t just about history; it also touches on geography (he knew in a very general way where India was, but clearly hadn’t met anybody who had been there). About India, he wrote: “In India live men of a spotted colour and there are found nightingales, elephants, pepper, precious stones, beryls, chalcedony, carbuncles, adamantine and hills of gold. Nevertheless it is impossible to go to them because of dragons and griffins.” On the other hand, he treated the earth being round as a settled fact, mentioning that you could see its round shadow on the moon during an eclipse.
The Polychronicon is an important book in the history of English (the language, that is), because at the time it was by no means clear that English would be the common language spoken in England. King Henry IV was the first English king after the Norman conquest who was a native English speaker. On the other hand, an act of Parliament in 1401 made it illegal to translate the Bible into English. The Polychronicon managed to get around this, though, because in 1387 it was translated into English (Higden had written it in Latin), and it contained numerous biblical stories and phrases.
The translator, John of Trevisa, added comments to the Polychronicon that say that French had been the main language used in teaching in England, after the Plague of 1348 that changed so that teaching in grammar schools was done in English.
There’s a passage in the Polychronicon that says: “Unto the tru knowlege of the kepynge of Ester, thre thynges ar to be attendide..the equinoccialle of ver, the perfite plenilune or fullenesse of the moone, and Sonneday.”
Have a look at that word “plenilune.” As Higdon explains, “plenilune means a full moon (or the time of the full moon). It’s from the Latin “plenilunium”, and it’s probably thanks to the Polychronicon that “plenilune” entered English. It’s an uncommon word, but a pretty nice one, and it’s been in occasional use ever since Higdon introduced it. In 1600: “Looke to thy braines least in the plenilune Thou waxe more madde.” in 1861: “Last Autumn we were four, and travelled far With Phoebe in her golden plenilune.” And by the 20th century you can find “plenilune” used by some pretty well-known authors, including James Joyce: “What counsel has the hooded moon Put in thy heart, my shyly sweet, Of love in ancient plenilune, Glory and stars beneath his feet.”
Later in the 20th century Umberto Eco used “plenilune” in Island of the Day Before: “You can see..when recur the Sundays and the Epacts, and the Solar Circle, and the Moveable and Paschal Feasts, and novilunes and plenilunes, quadratures of the sun and moon.” You might not be surprised; Eco wrote “The Name of the Rose”, a novel set in the time of Higdon, involving Benedictine monks (which Higdon was as well).
“Plenilune” also makes an appearance in Middle Earth (which evidently had a moon); Tolkein included it in The Adventures of Tom Bombadil:
“Of crystal was his habergeon,
his scabbard of chalcedony;
with silver tipped at plenilune
his spear was hewn of ebony.”
“Habergeon,” by the way, means an armored vest made of chain mail.
The next plenilune will be December 26, 2023, so you’ve got time to start using the word!
