Genkan (entrance) (玄関)
The word genkan refers to the main entrance of a building.
Originally 'genkan' was a Chinese term used in Taoism (in the Neidan, or spiritual alchemy method of Chinese alchemy, the genkan is the place where the ki [vital force that operates the body] first enters the body in order to circulate), and also a term used in Zen Buddhism (it is thought that when Daruma [Bodhidharma] brought Zen to Japan he directed that the word dhyana, meaning meditation, should be translated as "gen", which later became "zen"), and from these concepts 'genpinnokan' (gate leading to the road of genmyo [something black and not recognizable as to what it is but potentially spiritually deep]).
In Japan, a genkan was an entrance constructed in Shoin-zukuri style (a traditional Japanese style of residential architecture that includes a tokonoma), and in a kyakuden (guest hall) or hojo (abbot's chamber) at Zen temples. It was from the Edo Period that residential houses began to have genkan when shoin-zukuri became popular as a residential house.
Genkan and shoes
Many Japanese think that in Europe and the United States people do not take off their shoes at home, unlike the Japanese who take off their shoes in the genkan of most houses they enter. But, in the West too, people may take off their shoes depending on the region and the individual home.
In a wide area, taking in East Asia, South-East Asia and Turkey, it is a custom to remove shoes before entering a building. So, the custom of taking off shoes is not as unique as some Japanese think.