Mop Cap is a ladies indoor cap in white cotton with lace trim. A mobcap (or mob cap or mob-cap) is a round, gathered or pleated cloth (usually linen) bonnet consisting of a caul to cover the hair, a frilled or ruffled brim, and (often) a ribbon band, worn by married women in the Georgian period, when it was called a "bonnet". Source: https://en.wikipedia.org/wiki/Mobcap
Mop or Mob Cap