The word 'unnerving' is built upon the metaphorical use of 'nerve,' which evolved from the Latin nervus (sinew, tendon) to signify inner strength and fortitude in English. The prefix 'un-' systematically negates this core concept, creating the sense of "depriving of courage or strength." The suffix '-ing' then transforms this verbal action into an adjective describing the quality of causing such a loss. Thus, the literal morphemic logic—"making not have nerve"—directly maps onto the modern abstract meaning of inducing anxiety or fear.

Structure: un (not) + nerve (courage) + ing (adjective suffix) - un: A prefix of Germanic origin (Old English un-), meaning "not" or "the opposite of." It functions as a negator. - nerve: The core morpheme, from Latin nervus meaning "sinew, tendon; vigor, strength." In this context, it functions as the base noun meaning "courage, steadiness." - ing: A suffix of Germanic origin (Old English -ende, -ing), used to form present participles and adjectives from verbs, here indicating a quality or state.