Where does “南シナ海” come from?

南シナ海 (Japanese) comes from Japanese シナ, from Japanese 科, from Japanese 品, from Middle Chinese 品.

南シナ海 (Japanese): the South China Sea

Definitions

南シナ海 traces back through 3 separate lines of ancestry.

Step	Language	Word	Meaning
1	Japanese	シナ	Seriphidium cinum, syn. Artemisia cina: also known as santonica, Levant wormseed, and wormseed; an herbaceous perennial of the daisy family, historically used as a vermifugic anthelmintic (a drug to rid the body of parasitic worms)
2	Japanese	科	department, section; family; crime; wrongdoing
3	Japanese	品	article, goods; stock; quality
4	Middle Chinese	品	—

Step	Language	Word	Meaning
1	Japanese	南	the south; a southerly, south wind; to go south
2	Middle Chinese	南	—

Step	Language	Word	Meaning
1	Japanese	海	a sea, an ocean; a lake; an object covering over...
2	Old Japanese	うな	—