Jinjitsu is also called 'Nanakusa no Sekku[七草の節句（ななくさのせっく）]'(Nanakusa means seven herbs). This is because people eat Nanakusa-gayu[七草粥（ななくさがゆ）](rice porridge with chopped seven spring herbs) on the day.
Jinjitsu means 'Human Day'. In the ancient China, the first seven days of New Year(Shōgatsu[正月（しょうがつ）]) were allocated as Chick Day, Dog Day, Boar Day, Sheep Day, Ox Day, Horse Day, Human Day and the fortune-telling for the animal of the day was performed. People took care of the animal of each day and criminals were not punished on Jinjitsu, January 7th.
And there was a custom of eating a soup with seven kinds of vegetables to wish for the health on Jinjitsu. It was introduced into Japan in the Heian Period(794-1185) and changed into Nanakusa-gayu.
The word 'Nanakusa' is mainly used for seven herbs of spring(Haru no Nanakusa[春の七草]). They are usually called by traditional names. Haru no Nanakusa are as follows.
- Seri[芹（セリ）](water dropwort)
- Nazuna[ナズナ](shepherd's purse)
- Gogyō[ゴギョウ](Jersey cudweed, modern name: Hahako-gusa[ハハコグサ])
- Hakobe[ハコベ](common chickweed)
- Suzuna[スズナ] (turnip, modern name: Kabu[蕪（カブ）])
- Suzushiro[スズシロ](Radish, modern name: Daikon[大根（ダイコン）])
There are Nanakusa of autumn but they refers to the seven beautiful flowers of autumn(They are called 'Aki no Nanakusa[秋の七草]').
Nanakusa-gayu has been eaten to wish for the health as mentioned above and that is effective for overworked stomach by Osechi[御節（おせち）](Osechi are traditional dishes eaten in Shōgatsu.). But that is not eaten much now.