A powder room is a small bathroom that contains only a toilet and a sink. They are sometimes called guest bathrooms or half baths. There is no shower or tub in a powder room. They are almost always located on the first floor of a home.
The first floor positioning of powder rooms allows guests to utilize the facilities without feeling as though they have intruded in your home. The powder room is normally a very small room that is conveniently located and rarely contains a window.
Origin of the Term
The term powder room has been around since the 18th Century. It was considered a closet sized room where people applied extra powder to their wigs. The Victorian times kept the term "powder room" to discreetly excuse oneself.
Some women still refer to the half bath as the powder room, where "powdering your nose" was a phrase used again as a euphemism.