Gorenju was a title of honor used to indicate a legal wife of an aristocrat in Japan. After the Edo period, the Edo bakufu (Japanese feudal government headed by a shogun) put strict limitations on the use of the term.
Before the Edo Period
The term 'Gorenju' had not existed before the Nara period.
From the mid-Heian Period, it was an established custom for noble women not to show their faces to the opposite sex, even if it was their father or brother. It is believed that the etymology of 'Gorenju' came from the custom of women meeting people on opposite sides of a sudare (bamboo screen) or kicho (screen).
There is no literary work from the Heian period, however, that refers to a legal wife of an aristrocrat as a 'Gorenju.'
On the other hand, there have been documents found from the Sengoku period (period of Warring States) where the wife of Sengoku daimyo (Japanese territorial lord in the Sengoku period) was referred to as a 'Gorenju.'
The Edo bakufu went so far as to put the naming of a legal wife under the control of the daimyo (Japanese feudal lord). It is well-known that the term 'Midaidokoro' was limited to the legal wife of the Seii Taishogun (literally, "great general who subdues the barbarians"). Similarly, the prestigious term 'Gorenju' was limited to the wives of heirs to the Shogun and the Gosanke (three privileged branch families). However, in the case of Kodaiin, who later became the legal wife of Ienari TOKUGAWA, she was referred to as 'Goenjosama' at first, possibly because she was in such a delicate position.
Later on when Gosankyo (another three privileged branch families) was formed, the legal wives of Gosanke were also called 'Gorenju' due to the roles of Gosankyo being equivalent to the Gosanke.
Legal wifes of daimyo with over 100,000 koku crop yields were called 'Gozensama,' and those with less were called 'Okugata.'
Furthermore, in the case of a daughter of the Shogun becoming a legal wife, a completely different naming was arranged. She was called 'Goshudensama' when her husband's official rank was Jusanmi (Junior Third Rank) or higher, and 'Osumaisama' when Shoshiinojo (Senior Fourth Rank, Upper Grade) or lower.
This kind of naming became obsolete with the Meiji Restoration and collapse of the shogunate system.