Of the first water

 
To describe someone or something as being 'of the first water' is to indicate you hold them in the highest regard.


The phrase derives from the diamond industry. In the seventeenth century the degree of brilliance or lustre was described as its water and diamonds might be of the first water, second water and so on. Those of the first water were the finest and had the appearance of a clear, limpid stream. Although this method of grading diamonds died out in the first half of the nineteenth century the expression remains with us to this day.