Most of us have a busy life. Very busy. This leaves little time for winding down in the evening and 'preparing for bedtime'. At one time, a lady would take time to groom herself in the evenings before retiring to bed - often while wearing a peignoir. A peignoir is a long outer garment for women, often made of nylon and/or chiffon fabric. Frequently paired with a matching nightgown, they are a glamorous set of pajamas.
From the French word peigner, to comb the hair, a lady would wear this dressing gown while brushing her hair in the evening, specifically to cover the shoulders.
I think I will brush my hair tonight.