According to the Gesta Ungarorum (chapter: "Of the land of Ultrasilvana"), on reaching the Carpathian Mountains (~896), the Magyars found there three voivodeships: that of Menumorut in Crişana, of Glad in the Banat, and of Gelou in central Transylvania. Duke Gelou (Hungarian: Gyalu) is described as being a “certain Romanian”.
"And while they tarried there some while, Tuhutum father of Horca, as he was a shrewd man, when he learned from the inhabitants of the goodness of the land of Transylvania, where Gelou, a certain Vlach, held sway, strove through the grace of Duke Árpád, his lord, to acquire the land of Transylvania for himself and his posterity." (see the Remark, hereunder)
Gesta Ungarorum - written by Anonymi Bele Regis Notarii ('the anonymous notary of king Bela').
The chronicle was written probably between 1196 and 1203.
Anonymus was employed at the time of writing as a notarias, presumably in the court of Béla III of Hungary (1172–1196). He is most famous for his work Gesta Hungarorum ("The Deeds of the Hungarians"), written in Latin around 1100~1200. This work provides the most detailed history of the arrival of the Hungarians to the Carpathian Basin.
It is known from his Gesta Hungarorum that he was from the upper Tisza region and was closely connected to the Aba family of that region. In the preface, he wrote that he studied in Western Europe (probably Paris), where he learned the genre in which he wrote his Gesta.
Remark: The Tale of Bygone Years (Nestor's Chronicle ~1113) confirmed the statement of Anonymus:
"In the year 6406 (898), the Hungarians passed near Kiev, over the hill which is now called Ugor Koie, reached the Dnieper and they stretched their tents, because they were nomads as the Polovcs. Coming from the east, they went rushing through the high mountains, which were called Hungarian (the Carpathians) and they began to struggle with Volochs (Vlachs, Romanians) and Slavs who lived there. The Slavs were set there before and the Volochs conquered the country of the Slavs. But the Hungarians drove out afterwards the Volochs, they conquered the country and sat there together with the Slavs; since then the country is called Hungary."
Въ лето 6406. Идоша угри мимо Киевъ горою, еже ся зоветь ны не Угорьское, пришедъше къ Днепру, и сташа вежами; беша бо ходяще, аки се половци. Пришедъ от [въ]стока и устремишася чересъ горы великия, и почаша воевати на жиущая ту волхи и словени. Седяху бо ту преже словени, и волъхве прияша землю словеньску. Посемъ же угри прогнаша волъхи, и наследиша землю, и седоша съ словены, покоривше я подъ ся. Оттоле прозвася земля Угорьска.