Transylvania

Etymology tree
Proto-Indo-European *terh₂-
Proto-Indo-European *-t
Proto-Indo-European *térh₂t
Proto-Indo-European *-ónts
Proto-Indo-European *tr̥h₂ónts
Proto-Indo-European *tr̥h₂n̥ts
Proto-Italic *trāns
Proto-Italic *trāns-
Medieval Latin trans-
Proto-Indo-European *sel-der.?
Medieval Latin silva
Proto-Indo-European *-nós
Proto-Italic *-nos
Medieval Latin -nus
Medieval Latin -ānus
Medieval Latin silvānus
Proto-Indo-European *-yós
Proto-Italic *-ios
Old Latin -ios
Medieval Latin -ius
Medieval Latin -ia
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Hungarian Erdeuelucalq.
Medieval Latin Trānsylvānialbor.
English Transylvania
Learned borrowing from Medieval Latin Trānsylvānia, alternative spelling of Trānssilvānia, from trāns (“across”) + silvānus (“forest”, relational adjective) + -ia (abstract noun suffix), i.e. “region across the forest”, a calque of Hungarian Erdély, from erdő (“forest”) + elv/elü (“region beyond”). By surface analysis, tran- + sylvan + -ia.