Soap means:
(1) Short name of soap bucket (referring to oak, oak, etc. Its shell barrel can be dyed black by boiling juice, which is called "[oak seed]" and then "soap".
One day in the mountains, its plants are suitable for soap. -"Li Zhou Di Guan Da Situ"
(2) Another example is soap (such as oak chestnuts). Can be used as a black dye)
China Gleditsia sinensis
(3) A washing product is short for [soap]. Such as: soap; medicated soap
(4) the officers in the old yamen
The government sat in the third hall and asked the soap head on duty to bring the book in. -The Scholar