Citesc o biografie de-a lui Churchill în engleză și în contextul Primului Război Mondial e pomenită și România, dar numai cu denumirea Rumania, care m-a zgâriat pe creier de fiecare dată. Zilele acestea a apărut pe FB un film din arhiva Briths Pathe, cu imagini din Rumania, 1964.
Deja era un pic prea mult, așa că am devenit curios și am căutat pe net. Am găsit o explicație pe site-ul Orbis Latinus:
English uses both forms, Rumanian and Romanian, to denote the Romance-speaking population in the South-Eastern Europe north of the Danube, which was traditionally referred as Vlachs (or Wallachians). Both forms were adopted by the mid 19th century when the principalities of Wallachia and Moldova were unified to form a new state, Rumania or Romania. The forms Rumania and Rumanian were prevailing till the second half of the 20th century, when the forms with "o" gradually became more popular.
The form Rumân was the natural form used in Rumanian itself till the second half of the 19th century. The neighbouring languages (like Bulgarian, Serbian, Russian, Polish etc.) use the form with "u", and French for its part established the spelling Roumain, Roumanie. Spanish adopted the forms Rumania and Rumano and such was initially the practice in Italian. German has Rumänien, Rumäne and rumänisch.
The form with "o" was introduced in Rumania to stress the descendency of the Rumanians from the ancient Romans; this orthographic change happened by the time of the unification of the principalities of Wallachia and Moldavia in the unitary kingdom of Rumania. In this period Cyrillic script was replaced by Latin and the language was heavily re-latinized.
The Rumanian state since then always promote the spelling with "o", even in the foreign languages, and finally English also accepted it as official. Italian also changed the orthography, from "Rumania" to "Romenia"; modern Portuguese also uses the forms Romenia and Romeno.