From Wikipedia:

The earliest known reference to Transylvania appears in a Medieval Latin document of the Kingdom of Hungary in 1078 as ultra silvam, meaning “beyond the forest” (ultra meaning “beyond” or “on the far side of” and the accusative case of Sylva (sylvam) “woods, forest”). Transylvania, with an alternative Latin prepositional prefix, means “on the other side of the woods”. The Medieval Latin form Ultrasylvania, later Transylvania, was a direct translation from the Hungarian form Erdő-elve, later Erdély, from which also the Romanian name, Ardeal, comes. That also was used as an alternative name in German überwald (“beyond the forest”) (13th–14th centuries) and Ukrainian Залісся (Zalissia).

So it seems to be