The still room is a distillery room found in most great houses, castles or large establishments throughout Europe dating back at least to medieval times. The lady of the house was in charge of the room, where medicines were prepared, cosmetics and many home cleaning products created, and home-brewed beer or wine was often made. Herbs from the kitchen garden and surrounding countryside were processed into what today we call essential oils, and infused or distilled, or brewed (etc.) as required to make rose water, lavender water, peppermint based ointments, soaps, furniture polishes and a wide variety of medicines.  It was a working room: part science lab, part infirmary and part kitchen. In later years, as doctors & apothecaries became more widely spread and the products of the still room became commercially available, the still room became increasingly an adjunct of the kitchen. The use of still room devolved to making only jams, jellies, home-brewed beverages and as a store room for perishables such as cakes.
Originally, the still room was a very important part of the household, run by the lady of the house, and used to teach her daughters and wards some of the skills needed to run their own homes in order to make them more marriageable by having those skills. As practical skills fell out fashion for high born women, the still room became the province first of poor dependent relations, then of housekeepers or cooks. The still room was later staffed by the still room maid.