I always find it useful to look at the roots of words when starting a discussion. The first pace I usually look is in Joseph Shipley's The Origins of English Words: A Discursive Dictionary of Indo-European Roots. The entire entry is quoted below. The net of it is, as I understand it, is that a commons is something that is used together, always changes but remains one. A plurality that is also unitary. The first word listed is the fundamental Indo-European root word. The II means that there were two words spelled mei that had slightly different meanings.
mei II, expanded as meig, mein, melt: change, move away; exchange, arrange for services (hence applied to public office). Gk, amoeba (a negative): changes but remains one. am(o)ebean: alternately answering, as amoebean verses. The Saturday Review (London), 25 May 1861, spoke of an "amoebean exchange of witticism between the Bench and the Bar." In March, "Spring and Winter sing an amoebean song." amoebiform: like the Old Man of the Sea, protean. (The prophetic sea god who could change his shape at will, Proteus, is from Gk protos: first; see per 1. Proteus is also a genus of bacteria.) L, meatus; and via commeatus, Fr, conge, congee.
L mutare, mutatum: change. mutation. commute, commutations and permutations. permeate. irremeable. transmute; mutable, immutable. mutual. mew, mews, mo(u)lt. The verb mew was used of birds moulting: changing feathers. Then the plural form mews (now treated as a singular) was used of the buildings where the royal hunting hawks were kept; then of the royal and noble stables on such grounds. Many short lanes and London streets today are thus called mews.
Also, common: used together. The Common: ground owned by the community, usually a central square of grass, in early days used for grazing. The Commons: British Lower House of Parliament, representatives of the "common people." communicate, excommunicate. communism, coined in 1840 by Goodwyn Barmby, who in 1841 founded the London Communist Propaganda Society. Karl Marx wrote his Communist Manifesto in 1847; in 1849 he came to London to study in the Museum Library, publishing the first volume of Das Kapital in 1867.
Hence, too, community and commune. municipal, municipality: first, a Roman town with its own regulations (munia capere: to hold [its own] services). munificent. remuneration. immune; immunity, immunology. Also migrate, emigrate, immigration; transmigration. remuda, on the western ranch. Gc gamaidans: badly changed; wounded. mad, maim, mayhem; mean. bemean, virtually supplanted by demean; see men II.
If you can talk with crowds and keep your virtue,
Or walk with kings, nor lose the common touch . . .
If you can fill the unforgiving minute
With sixty seconds worth of distance run,
Yours is the earth, and everything that's in it,
And-which is more-you'll be a man, my son.
"Adieu to common feeling, common prudence and common sense!" - Rev. Sydney Smith (d. 1845)
"Common sense is most uncommon sense."