Source : Webster's Revised Unabridged Dictionary (1913)

   3. The reticulated headdress or net, made of gold or silver
      wire, in which ladies in the Middle Ages confined their
      hair.

            A fret of gold she had next her hair. --Chaucer.

   {Fret saw}, a saw with a long, narrow blade, used in cutting
      frets, scrolls, etc.; a scroll saw; a keyhole saw; a
      compass saw.