The word "prematurest" is a superlative form of the adjective "premature". The etymology of "premature" can be traced back to the Latin roots "prae" meaning "before" and "maturus" meaning "ripe" or "timely". In Middle English, the word appeared as "prematoure", which eventually evolved into "premature" in modern English. The superlative form "prematurest" adds the suffix "-est" to indicate the highest degree of prematurity.