the word "unreadable" is a modern english formation built from native and borrowed elements. the core verb "read" originates from old english rǣdan, which carried a broader sense of "to advise, interpret, discern," evolving specifically to mean interpreting written text. the negative prefix "un-," from old english, is one of the most common and productive means of forming opposites. the suffix "-able," entering english via old french from latin -abilis, attaches to verbs to create adjectives meaning "capable of being [verbed]." therefore, the literal morphemic construction "not capable of being read" logically yields the modern meanings of illegibility or lack of literary merit.

Structure: un (not) + read (to read) + able (capable of) un- (old english, a prefix meaning "not"); read (old english, a verb meaning "to interpret written symbols"); -able (latin via old french, an adjective-forming suffix meaning "capable of, fit for").