the word 'unfeasible' is a relatively modern english formation, first appearing in the 17th century. it is constructed by combining the negative prefix 'un-' with the adjective 'feasible'. 'feasible' itself entered english from middle french 'faisable', which derives from the verb 'faire' (to do), tracing back to the latin verb 'facere'. the suffix '-ible' is a latin adjectival ending indicating capability. therefore, the literal morphemic construction "not + able to be done" directly and logically yields the modern abstract meaning of something that is not practicable or capable of being accomplished.

Structure: un (not) + feas (do, make) + ible (able to be) - un: a prefix of germanic origin (old english) meaning "not". - feas: a root derived from the middle english 'fesen', from old french 'fes-', 'fais-' (stem of 'faire' meaning "to do, make"), ultimately from latin 'facere' ("to do, make"). its functional role is to carry the core meaning of "doing" or "making". - ible: a suffix from latin '-ibilis', meaning "able to be". it forms adjectives indicating capacity or worthiness.