The word "unexpired" is built upon the verb "expire," which originates from the Latin exspirare, meaning "to breathe out" or "to die" (as in one's last breath). This Latin term combines ex- ("out") and spirare ("to breathe"). Over time, the meaning extended metaphorically to signify the end or termination of a period, such as a lease or a license, much like the final breath ends life. The prefix un- is then added to negate this sense, creating an adjective that describes something which has not yet breathed its last—that is, something still in force and not yet terminated.

Structure: un (not) + ex (out) + pired (breathed) - un: A prefix of Germanic origin (Old English) meaning "not," used to form negatives. - ex: A prefix from Latin, meaning "out of, from, former." - pired: Derived from the Latin verb spirare (to breathe), via the past participle form spiratus, which evolved into the English verb "expire."