unbreakableness

Etymology tree
Proto-Indo-European *né
Proto-Indo-European *n̥-
Proto-Germanic *un-
Proto-West Germanic *un-
Old English un-
Middle English un-
English un-
Proto-Indo-European *bʰreg-der.
Proto-Germanic *brekaną
Proto-West Germanic *brekan
Old English brecan
Middle English breken
English break
Proto-Indo-European *-tḗr
Proto-Indo-European *-dʰlom
Proto-Indo-European *-dʰlis
Proto-Italic *-ðlis
Latin -bilis
Latin -ābilis
Old French -ablebor.
Middle English -able
English -able
English unbreakable
Proto-Germanic *-in-
Proto-Indo-European *-h₂
Proto-Indo-European *-éh₂
Proto-Indo-European *-yéti
Proto-Indo-European *-eh₂yéti
Proto-Indo-European *-h₂ti
Proto-Germanic *-ōną
Proto-Germanic *-inōną
Proto-Indo-European *-dyé-
Proto-Germanic *-atjaną
Proto-Indo-European *-tus
Proto-Germanic *-þuz
Proto-Germanic *-assuz
Proto-Germanic *-inassuz
Proto-West Germanic *-nassī
Old English -nes
Middle English -nesse
English -ness
English unbreakableness
From unbreakable + -ness.