Shi shi (or shi-shi) is a slang term of Japanese origin that conveys generally two different meanings.
The first meaning is primarily used in Hawaiian slang, and it simply means to urinate, or to defecate.
It is used as an informal but restrained way to signal you need to hit the restroom: “I need to shi shi.”
The more popular meaning of shi shi, however, is when it’s used as an adjective.
It is said about people, places or objects that are either really fancy or even too extravagant in appearance.
This version of the expression can convey both negative or positive connotations, depending on the context.
The ascendant of the slang can be found in the Japanese language, where “Shi-shi” is a very versatile term.
It can mean a wide variety of different things, however, it is unknown when it was adopted to pidgin English.
As mentioned above, shi shi is used commonly in Japanese, but it can be found in a number of other East-Asian languages as well.
Both meanings of the slang term started to spread in Hawaiian Creole initially, and later migrated into American English as well.