noun
highest-ranking prostitute in Edo's Yoshiwara district (Hōreki era onward)
Archaic term specific to the Yoshiwara red-light district during the Edo period, used from the Hōreki era (1751–1764) onward. Not used in modern Japanese.
See also: 宝暦
江戸の吉原では、昼三は宝暦以降の最高位の遊女を指した。
In Edo's Yoshiwara, 'chūsan' referred to the highest-ranking courtesan from the Hōreki era onward.
太夫 was the highest rank of courtesan in earlier periods and in other districts like Kyoto's Shimabara, while 昼三 was specific to Yoshiwara from the Hōreki era.
The exact derivation is uncertain; the term is a historical designation for a rank of courtesan in Edo-period Yoshiwara.