The word 'unacquainted' is built upon the core verb 'acquaint', which entered English via Old French from the Latin 'accognitare', meaning "to make known." This Latin verb itself is a frequentative form of 'ad cognoscere', literally "to come to know." The Germanic negative prefix 'un-' is attached to negate the state, and the adjectival suffix '-ed' is added, indicating the condition of not having been made known or familiar. Thus, the literal morphemic construction "not + made known + (adjective)" directly yields the modern abstract meaning of lacking familiarity or knowledge.

Structure: un (not) + acquaint (make known) + ed (adjective suffix) - un: A prefix of Germanic origin (Old English) meaning "not," used to form negatives. - acquaint: A verb from Old French 'acointer', based on Latin 'accognitare', from 'ad-' (to) + 'cognoscere' (to know). - ed: A suffix of Germanic origin (Old English) used to form adjectives from verbs or nouns, indicating a state or condition.