Etymology tree Proto-Indo-European *né Proto-Indo-European *n̥- Proto-Italic *n̥- Latin in-bor. Middle English in- English in- English express Proto-Indo-European *-tḗr Proto-Indo-European *-dʰlom Proto-Indo-European *-dʰlis Proto-Italic *-ðlis Latin -bilis Latin -ibilis Old French -ibleder. Middle English -ible English -ible English expressible English inexpressible From in- + expressible.