acoustical

Etymology tree
Proto-Indo-European *h₂eḱ-
Proto-Indo-European *h₂ew-
Proto-Indo-European *-s
Proto-Indo-European *h₂ṓws
Proto-Indo-European *-yéti
Proto-Indo-European *h₂ḱh₂owsyéti
Proto-Hellenic *akóuhō
Ancient Greek ἀκούω (akoúō)
Proto-Indo-European *-kos
Ancient Greek -κός (-kós)
Ancient Greek -ῐκός (-ĭkós)
Ancient Greek ᾰ̓κουστῐκός (ăkoustĭkós)bor.
Medieval Latin acousticusbor.
English acoustic
Proto-Indo-European *h₂el-der.?
Proto-Italic *-ālis
Latin -ālisbor.
Old French -albor.
▲
Latin -ālis
Old French -elbor.
▲
Latin -ālisbor.
Middle English -al
English -al
English acoustical
From acoustic + -al.