У англосаксов King этимологически близок kin, что есть родня. Поэтому и подвластные воспринимались как единый род. Отсюда неразличение родов, не народ, а Nation, что этимологически тоже подразумевает единый корень происхождения. Под властью Короля, значит, автоматом единая нация. С другой стороны, и на Nation переносилось значение единства подвластности. Здесь, в самом языке,  генезис Nation как Nation-State, а не в "Общественном договоре".  Что поделать, дикари. Если бы у нас был не Царь, а какой-нибудь Отцерод, в России тоже была бы давно нация, а не народ.

Не настаиваю. Но такое именно у меня впечатление сложилось по результатам поверхностного беглого поиска. Однако ничего не нашел о нациях крупных собственников и вольных средневековых ландскнехтов.

English Etymology Dictionary
nation 13c., from O.Fr. nacion, from L. nationem (nom. natio) "nation, stock, race," also "that which has been born," from nasci "be born." Political sense has gradually taken over from meaning "common ancestry." Nationalism is first attested 1836 as "the doctrine of divine election of nations;" 1844 in meaning "devotion to one's nation;" earliest in an Irish context.

Websters 1828 Dictionary:    
Nation NATION, n. [to be born]
    1. A body of people inhabiting the same country, or united under the same sovereign or government; as the English nation; the French nation. It often happens that many nations are subject to one government; in which case, the word nation usually denotes a body of people speaking the same language, or a body that has formerly been under a distinct government, but has been conquered, or incorporated with a larger nation. Thus the empire of Russia comprehends many nations, as did formerly the Roman and Persian empires. Nation, as its etymology imports, originally denoted a family or race of men descended from a common progenitor, like tribe, but by emigration, conquest and intermixture of men of different families, this distinction is in most countries lost.
    2. A great number, by way of emphasis.

Webster's Revised Unabridged Dictionary (1913):
Nation \Na"tion\, n. [F. nation, L. natio nation, race, orig., a being born, fr. natus, p. p. of nasci, to be born, for gnatus, gnasci, from the same root as E. kin. [root]44. See Kin kindred, and cf. Cognate, Natal, Native.] 1. (Ethnol.) A part, or division, of the people of the earth, distinguished from the rest by common descent, language, or institutions; a race; a stock. All nations, and kindreds, and people, and tongues. --Rev. vii. 9. 2. The body of inhabitants of a country, united under an independent government of their own. A nation is the unity of a people. --Coleridge. Praise the power that hath made and preserved us a nation. --F. S. Key. 3. Family; lineage. [Obs.] --Chaucer. 4. (a) One of the divisions of university students in a classification according to nativity, formerly common in Europe. (b) (Scotch Universities) One of the four divisions (named from the parts of Scotland) in which students were classified according to their nativity. 5. A great number; a great deal; -- by way of emphasis; as, a nation of herbs. --Sterne. Five nations. See under Five. Law of nations. See International law, under International, and Law. Syn: people; race. See People.

Merriam-Webster's Collegiate Dictionary, 11th Edition (2003):
nation noun Etymology: Middle English nacioun, from Anglo-French naciun, from Latin nation-, natio birth, race, nation, from nasci to be born; akin to Latin gignere to beget — more at kin Date: 14th century 1. a. (1) nationality 5a (2) a politically organized nationality (3) a non-Jewish nationality <why do the nations conspire — Psalms 2:1 (Revised Standard Version)> b. a community of people composed of one or more nationalities and possessing a more or less defined territory and government c. a territorial division containing a body of people of one or more nationalities and usually characterized by relatively large size and independent status 2. archaic group, aggregation 3. a tribe or federation of tribes (as of American Indians)

Websters 1828 Dictionary:
King KING, n.
1. The chief or sovereign of a nation; a man invested with supreme authority over a nation, tribe or country; a monarch. Kings are absolute monarchs, when they possess the powers of government without control, or the entire sovereignty over a nation; they are limited monarchs, when their power is restrained by fixed laws; and they are absolute, when they possess the whole legislative, judicial, and executive power, or when the legislative or judicial powers, or both, are vested in other bodies of men. Kings are hereditary sovereigns, when they hold the powers of government by right of birth or inheritance, and elective, when raised to the throne by choice. Kings will be tyrants from policy, when subjects are rebels from principle.

English Etymology Dictionary: 
king O.E. cyning, from P.Gmc. *kuninggaz (cf. Du. koning, O.H.G. kuning, O.N. konungr, Dan. konge, Ger. k?nig). Possibly related to O.E. cynn "family, race" (see kin), making a king originally a "leader of the people;" or from a related root suggesting "noble birth," making a king originally "one who descended from noble birth." The sociological and ideological implications make this a topic of much debate. Finnish kuningas "king," O.C.S. kunegu "prince" (Rus. knyaz, Boh. knez), Lith. kunigas "clergyman" are loans from Gmc. In O.E., used for names of chiefs of Anglian and Saxon tribes or clans, then of the states they founded. Also extended to British and Danish chiefs they fought. The chess piece so called from 1411; the playing card from 1563; use in checkers/draughts first recorded 1820. Applied in nature to species deemed remarkably big or dominant (e.g. king crab, 1698), "As leon is the king of bestes." [John Gower, "Confessio Amantis," 1390] Kingfisher (1440) was originally king's fisher, for obscure reasons. Kingdom-come "the next world" (1785) is from the Lord's Prayer. The film "King Kong" was released 1933.

Webster's Revised Unabridged Dictionary (1913):
Kin \Kin\, n. [OE. kin, cun, AS. cynn kin, kind, race, people; akin to cennan to beget, D. kunne sex, OS. & OHG. kunni kin, race, Icel. kyn, Goth. kuni, G. & D. kind a child, L. genus kind, race, L. gignere to beget, Gr. ? to be born, Skr. jan to beget. ?. Cf. Kind, King, Gender kind, Nation.] 1. Relationship, consanguinity, or affinity; connection by birth or marriage; kindred; near connection or alliance, as of those having common descent. 2. Relatives; persons of the same family or race. The father, mother, and the kinbeside. --Dryden. You are of kin, and so a friend to their persons. --Bacon.