A plain cap or headdress for women or girls, especially one tied under the chin by a very broad band
She was dressed entirely in flowing black cerements and wore a little lacy mob-cap on a mass of dead-looking yellowish white hair; her features were still beautiful, but her face was completely covered with mauve face-powder.
a light cotton hat with a decorative edge, worn by women in the 18th and 19th centuries (Probably from mab, mob (16-18 centuries), from the female name Mab, from Mabel)