Mid 16th century (in an earlier sense). As noun from classical Latin postrēmus person who is last, postrēmum thing which is last, uses as noun of masculine and neuter respectively of postrēmus, adjective; as adjective from classical Latin postrēmus last (in space or time), superlative of posterus later, next, formed on the model of suprēmus, superlative of superus. With use as adverb compare classical Latin postrēmō, postrēmum, adverbs, originally ablative and accusative respectively of the neuter of postrēmus.