We don't have synonyms for dernier yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are vernier, denier and bernier.
°A unit of weight which indicates the fineness of fiber or yarn; that is equal to one gram per 9000 meters. It is especially used to measure or indicate the fineness of hosiery.
°A unit of weight which indicates the fineness of fiber or yarn; that is equal to one gram per 9000 meters. It is especially used to measure or indicate the fineness of hosiery.