The word 'unknowability' is a modern philosophical compound built from layered English morphemes. Its core, 'know,' descends from the Proto-Germanic knēaną, related to concepts of perception and recognition. The prefix 'un-,' an ancient and prolific negator from Proto-Indo-European n̥-, systematically reverses the state described. The suffix '-ability,' entering English via Old French from Latin -abilitās, transforms the negated verb into an abstract noun denoting a permanent quality or condition. Thus, the literal construction "not-know-capacity" elegantly conceptualizes the inherent limitation or quality of being beyond the reach of knowledge, a term central to discussions of metaphysics and epistemology.

Structure: un (not) + know (to have knowledge of) + ability (capacity or quality) - un: A prefix of Germanic origin (Old English un-), meaning "not." It functions as a negative particle. - know: A verb root of Germanic origin (Old English cnāwan), meaning "to perceive, to be aware of." It functions as the core lexical base. - ability: A noun-forming suffix of Latin origin (from -abilitās), meaning "capacity, quality, or state of being." It functions as a nominalizer.