Joshi (also called Jomi) is one of five seasonal festivals. It is a festival celebrated on March 3. It is also called Momo no Sekku (the Peach Festival) since peach trees are usually in full bloom on March 3 according to the lunar calendar.
'Hina-matsuri' (the Doll's Festival) is considered to have originated in 'Hina-asobi' (literally, 'playing with hina dolls') during the Heian period where children of nobility in Kyoto used to play with models of the imperial palace and decorations.
Later, Hina-asobi also became popular within the buke shakai (the society of samurai families) and then during the Edo period, commoners playing with dolls was associated with seasonal festivals to form an event of season which developed into the Hina Festival or 'Hina-matsuri.'
Later, the Hina-matsuri Festival turned out to be a rite or festival to purify people and prevent the causes of disaster by removing various stains from katashiro (a small human-shaped sheet of paper) by floating them in streams, rivers, or in the sea. Even now, this custom is still observed as a festival called 'Nagashi-bina' (literally, 'floating hina dolls').
Originally, the Hina-matsuri Festival was run for both boys and girls along with Tango no Sekku (the festival on May 5 of the lunar calendar), but from around the Edo Period, gorgeous hina dolls were regarded as belonging to girls while Tango no Sekku became recognized as the Boys Festival because of its alias name, Shobu no Sekku (literally, the Iris Festival), of which the word 'Shobu' is pronounced in the same way it is for the different Shobu, meaning victory or defeat.
The term 'Joshi' or 'Jomi' means the day of the Serpent (the sixth sign of the Chinese zodiac) in the beginning of the month, and it had originally indicated the day of the Serpent in March, but it is reported that, after the Wei dynasty (Three States Period) in ancient China, the Joshi Festival became celebrated on March 3.
In ancient China, people practiced the custom of making ablutions in the river to purify their bodies and expel the unclean on the day of Serpent that took place during the beginning of a month, and this was called Joshi no Harai (literally, purification performed on the earliest day of the Serpent in a month). This custom was introduced to Japan in the Heian Period.