Middle English: from Old French diapre, from medieval Latin diasprum, from medieval Greek diaspros (adjective), from dia ‘across’ + aspros ‘white’. The term seems originally to have denoted a costly fabric, but after the 15th century it was used as in diaper (sense 2 of the noun); babies' nappies were originally made from pieces of this fabric, hence diaper (sense 1 of the noun) (late 16th century)