This post, we pick up on the food groups, looking at dairy, protein, and oils.
Dairy
Dairy is the kind of word that makes etymology nerds like me jump up and down. It features disguised compounds. When words get smashed together with other words, sounds change and forms change, sometimes making one word look like another, other times burying a compound altogether. As the preeminent etymologist Anatoly Liberman puts it, “compounds tend to deteriorate.”
Dairy is a full-fat example of this.
In Middle English, the word dairy took the form deierie, joining dey (among other forms) and the suffix –ery. Dey first referred to a “female servant.” Later, it meant a “farm servant” and “dairymaid.” The suffix -ery can denote the place of a particular activity, Here, a dairy was originally the room or building “for treating milk and its products” (Oxford Dictionary of English Etymology [ODEE]). Think bakery or laundry for some –ery comparisons.
There is much to unpack in terms of the historic constructions of women and work implied in dey, but, on an etymological level, what’s going?
Dey is from the Old English dæge, a “female servant,” but, literally, it meant a “kneader of bread.” The word is rolled out from the Proto-Germanic *daigjon; the sense of “kneading” is at root. The product of kneading, dough is a cognate. If we knead this *daigjon further, we find a Proto-Indo-European root *dheigh, meaning, according to Jordan Shipley, everything from “knead” and “mix dough” to “shape clay” and “put together.”
Human tongues have shaped some other fascinating forms out of this *dheigh, but we’ll save them for next post.
Protein
Protein: the building blocks of life and, as a coinage, an example of one of the building blocks of etymology. In an 1838 article in Bulletin des sciences physiques et naturelles en neerlande, Dutch scientist Gerhard Johan Mulder uses a French formation, protéine, to describe the composition of some organic substances. Apparently, this word was the suggestion of Jöns Jacob Berzelius, the accomplished Swedish chemist, who is also given credit for polymer and catalysis, among other terms.
So, why protéine? At root is the Greek proteios, “of the first quality,” joining protos (“first”) and the -eios suffix. It was so named as a “primary substance…of material bodies of animals and plants” (Oxford English Dictionary).
Proto- is a member of the big family headed by the Proto-Indo-European *per-, which came to mean everything from “through” and “around” to “before” and “first.” Per-, peri-, para-, and pro- may all be familiar prefixes derived from it. They are still productive today.
Our understanding of protein has evolved, to be sure, for now protein is considered one of the three food groups in Orange County, CA. The others being, of course, juice (i.e., blended juices and smoothies) and Starbucks.

Oil
Health advice aside, even etymology is urging you to use olive oil as your cooking oil. For oil, etymologically, is olive oil.
Oil, whose historic spellings are more varied than your choices of olive oil at the grocery store, is from the Old and Middle French oile, pressed from the Latin oleum. It referred to “oil,” thus “olive oil.” Old English had ele, a cognate of oil, but Germanic languages jumped on the Latin oleum food craze, and a new brand, if you will, made it into the pantry.
The Latin oil goes further back to the Greek elaion, the “olive tree” or “olive.” The Romans took elaion up as oliva, hence olive. The Online Etymology Dictionary speculates that the Greek root might be related to the Armenian ewi, “oil,” adopted into Greek from Aegean or Cretan tonuges. Aremenian is indeed an Indo-European language with some kinship to Ancient Greek. Wiktionary seconds this ewi cognate, adding the Old Church Slavonic’s loi, “tallow,” and posits a Proto-Indo-European *loiwom.
Petroleum is literally “rock oil,” joining the Latin petra (rock, via Greek) and oleum (as discussed above). Shipley observes that petroleum was “first extracted from fissures in rock.” Margarine is short for oleomargarine. The oleo- refers to “oil,” of course, and the margarine refers to “margaric acid,” named from the Greek margarites, “pearly,” for the acid’s crystal’s “pearly lustre” (ODEE). And now you know why a Margaret is so named.
Next post, we’ll pick up on *dheigh, including the surprising origins of lady and lord.