Q: What is the purpose of the “-er” suffix in “shoulder”? Is it a comparative (as in “stronger”) or an agent (as in “farmer”). And is “shoulder” related to “shield,” as some suggest?
A: The “-er” in “shoulder” is not a suffix. It’s merely part of the word. And while it seems likely that “shoulder” has some distant connection with “shield,” there’s no evidence to prove it.
“Shoulder” was recorded as far back as the 600s in early Old English, where it was spelled variously as sculdur, sculdor, sculder, and scyldur.
The word came into English by way of old West Germanic languages, in which it had two syllables and ended in –er or –ra (the modern German is schulter), according to the Oxford English Dictionary.
The earliest known use of “shoulder” in English writing, the OED says, comes from The Epinal Glossary, a book of Latin terms translated into Old English.
The glossary, which dates from sometime before 700, has this entry: “Scapula, sculdur.” (In Late Latin, scapula meant shoulder; in English “scapula” has always meant shoulder blade.)
Another word from Germanic, “shield,” first appeared in English writing more than a century later, about 825, in a passage from The Vespasian Psalter:
“Ðer gebrec hornas bogan sceld sweord & gefeht” (“The clamor of horns, bows, shield, sword, and fighting”).
Now for their etymologies.
The OED traces “shoulder” to a prehistoric West Germanic term reconstructed as skuldr-, and it traces “shield” to another prehistoric Germanic root, skelduz-.
These may sound similar, but the OED doesn’t connect them. As the editors say, “the affinities of the West Germanic word [skuldr-] are disputed.”
But another source, John Ayto’s Dictionary of Word Origins, does mention a possible link: “One suggestion is that it [skuldr-] is distantly related to English shield, and originally denoted ’shoulder blade’ (the underlying meaning being ‘flat piece’).”
This is plausible but difficult to prove, since even before prehistoric Germanic, “shoulder” and “shield” were represented by different roots.
Language scholars have identified the source of “shoulder” as an ancient Indo-European root, skep– (to cut or scrape), and the primitive ancestor of “shield” as skel– (to cut).
(These roots, from before written language, are rendered differently by some scholars. We’ve used spellings from The American Heritage Dictionary of Indo-European Roots.)
What do shoulders have to do with cutting and scraping?
Some etymologists suggest that shoulder blades, perhaps from animals, were used as tools for scraping.
Others speculate that the anatomical term may have originally referred to spades or shovels, and that shoulders were named for their resemblance to those flat, sharp implements.
What does a shield have to do with cutting? In Germanic the original sense, as Ayto writes, may have been “a flat piece of wood produced by splitting a log, board.”
If there is a link connecting “shoulder” and “shield,” some common ancestor beginning with ske-, perhaps new evidence will eventually come to light and etymologists will connect the dots.
One thing is certain about these very old words. They’ve kept their original literal meanings since they entered English some 1,500 years ago—“shoulder” as the anatomical part and “shield” as the defensive weapon.
They’ve become verbs and adjectives as well as nouns, and over the centuries they’ve developed scores of figurative and extended meanings, both alone and in phrases.
To choose just one example, would you believe that “cold shoulder,” in the sense of coldness or indifference, is 200 years old?
The OED’s earliest citation is from The Antiquary (1816), a novel by Sir Water Scott: “The Countess’s dislike did na gang farther at first than just shewing o’ the cauld shouther.”
from Grammarphobia http://www.grammarphobia.com/blog/2016/08/shoulder.html