Transylvania has had different names applied to it in several traditions.
''Transylvania''
The first reference to the region was as the Medieval Latin expression terra ultra silvam in a document dating to 1075. The expression Partes Transsylvanæ appears in the 12th century in Legenda Sancti Gerhardi and subsequently as Transsilvania in medieval documents of the Hungarian kingdom.
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The names of Ardeal in Romanian and Erdély in Hungarian are believed to be connected. However, the original source and meaning are disputed and claimed by both Romanians and Hungarians. The first Hungarian form recorded was Erdeuelu while the first Romanian form recorded was in 1432 as Ardeliu. The initial a/e difference between the names can be found in other Hungarian loans in Romanian, such as Hungarian egres ‘gooseberry’ → Romanian agriș, agreș, as well as in placenames, e.g., Egyed, Erdőd, Erdőfalva, Esküllő → Adjud, Ardud, Ardeova, and Așchileu.
Hungarian view
The consensus of Hungarian linguists and Hungarian historians on the etymology of both Erdély and Transylvania is as follows:
The modern Hungarian form Erdély was derived from Erdő-elü, literally ‘beyond the forest’. means ‘woods, forest’, and the archaic elüsuffix meant ‘beyond’ and was applied to a type of border region and the associated social and economic organisation; for example, Gyepűelve, and archaic Havaselve ‘Wallachia’, lit. "beyond the snowy mountains", refers to a region lying beyond the Carpathian mountains if viewed from Hungary, and was under strong Hungarian political influence during the Middle Ages. If viewed from Hungary, Erdő-elü probably refers to the fact that the Transylvanian plateau is separated in the northwest from the Great Hungarian Plain and Crișana plains by the well-forested Apuseni mountains. Alternatively, from the point of view east of the Carpathians, the name could suggest that the Hungarian name was created in Etelköz/Atelkuzu, prior to settling on the Hungarian plain.
The Medieval Latin form Ultrasylvania, later Transylvania, was a direct translation from the Hungarian form. This theory is also supported by the Romanian historian Ioan-Aurel Pop.
Romanian view
Several Romanian perspectives have suggested alternative etymologies:
A letter from around 960 from the Khazar king Joseph to Chasdai ibn Shaprut, the rabbi of Córdoba, mentions the "Ardil country", rich in gold and silver. Today, in Hebrew, Ardeal is written identically: ארדיל. This theory therefore suggests that Ardil was the primary form of the name, thus "Ardeal" is an original Romanian toponym.
''Siebenbürgen''
The oldest occurrences of this form are from the 13th century:
In the year 1241: in Annales Sancti Trudperti and in the Annals of Zwifalt: "Tartari terras Pannonie, Septum urbium, Moraviae vestaverunt”
In the year 1242: in the notes of the friar Erfurt: "Eodem anno Tartari in Ungaria, terra scilicet Septem castrorum, civitatem dictam Hermanii villam in Aprili expugnantes, usque ad centum ibi peremerunt...”
In the year 1285: "Eodem anno Tarthari terram Ungarie que dicitur Septemcastris, intraverunt et multos christianos captivaverunt et occiderunt” and "...quid audientes Septemcastrenses”.
In the year 1296: a reference to a particular "maister Dietrich von Siebenbuergen”.
In the year 1300: Ottacher of Styria mentions "Sybenburger”.
There exist a number of theories on the etymology of Siebenbürgen, the German name for Transylvania. The most widely accepted theory is that Siebenbürgen refers to the seven principal fortified towns of the Transylvanian Saxons. The name first appeared in a document from 1296. An alternate Medieval Latin version, Septem Castra was also used in documents. The towns alluded to are Bistritz, Hermannstadt, Klausenburg, Kronstadt, Mediasch, Mühlbach, and Schässburg. Other theories include:
Siebenbürgen means "Seven Castles" but does not refer to the towns of the Transylvanian Saxons. Transylvania and the Mureș valley seem to have been the first portion of land within the Carpathians where Magyars gained a foothold. According to legend, each of the seven Magyar chieftains erected an earthen 'castle' in this region.
Siebenbürgen means explicitly "Seven Towns" or "Seven Castles". However, this etymology seems to originate in the dialectical tradition of the first, mainly Low German, Flemish and Dutch settlers, in whose homelands there are hilly regions called "Zevenbergen" and "Sevenbergen".
Saxon settlement in Transylvania began in Sibiu. An early German name for the town was Cibinburg. The alternate name Cibinburg was corrupted into Siebenbürgen, and became the name for the whole region.
