Q: How did the digestion of food come to mean a digest of information?
A: You’ll be surprised to hear this, but the two senses showed up in English about the same time, and the Latin source for both referred to the digesting of information, not food.
When the word “digest” appeared in Middle English in the late 1300s, it was a noun for “a summary of Roman laws better known as the Justinian Code,” according to the Chambers Dictionary of Etymology.
In Latin, Chambers says, a dīgesta was “a collection of writings arranged under headings.” The ultimate source is the Latin verb dīgerĕre (to separate, divide, distribute, arrange).
The earliest citation for the noun “digest” in the Oxford English Dictionary is from John Trevisa’s translation, dated sometime before 1387, of Ranulf Higden’s Polychronicon: “Iustinianus [Justinian] … made and restored þe [the] lawes of digest.”
The noun “digestion” showed up around the same time in the food sense. The first OED example is from Chaucer’s The Canterbury Tales (circa 1386). In “The Squire’s Tale,” sleep is described as “the Norice [nurse] of digestioun.”
How did a Latin term for arranging information give English a word for digesting food?
John Ayto, in his Dictionary of Word Origins, says that the “divide” and “distribute” meanings of the Latin verb evolved in English into the sense of “dissolve,” as in “dissolve and obtain nutrients from food in the body.”
When the verb “digest” first appeared in the late 1400s, it meant to classify things, usually by condensing them, or to “prepare (food) in the stomach and intestines for assimilation,” according to the OED.
The first Oxford citation for the verb’s classification sense is from The Revelation to the Monk of Evesham (1482): “He told thees thynges the whiche here after be digestyd and wreten.”
The dictionary’s first example for the verb’s nutritional sense is from the Catholicon Anglicum (c. 1483), an English-Latin wordbook: “To Digeste, digerere.” We checked the original text, but those are the only three words in the entry.
Here’s a clearer example from Pylgrimage of Perfection, a religious treatise by William Bonde written sometime before 1530: “Baskettes of breedes [breads], that they coude not eate & digest.”
In the mid-1500s, the noun “digest” took on its modern sense of a “digested collection of statements or information; a methodically arranged compendium or summary of literary, historical, legal, scientific, or other written matter.”
The earliest OED example is from Lydgate’s Auncient Historie (1555), edited by John Braham: “The verye trouthe therof is not to be had in theyr dygestes.”
Braham’s version is the second edition of Troy Book, a Middle English poem written by John Lydgate in the early 1400s and first printed in 1513.
Finally, here’s an example from a March 24, 1789, letter in which Thomas Jefferson gives his opinion on Voyage du Jeune Anarcharsis en Grèce (Travels of Anacharsis the Younger in Greece), by the French writer and antiquarian Jean-Jacques Barthélemy:
“This is a very elegant digest of whatever is known of the Greeks.”
from Grammarphobia http://www.grammarphobia.com/blog/2017/05/digest.html