Kōchi (city, prefecture)
Refers to Kōchi City or Kōchi Prefecture on Shikoku island. Context usually makes the distinction clear.
Kōchi is in Shikoku.
Kōchi Prefecture is famous for seared bonito.
高知 is the proper name of a Japanese prefecture, sharing the exact same pronunciation as the common noun 高地 meaning 'highlands'.
The name 高知 (Kōchi) is a place name; its historical derivation is uncertain.