Based on the provided source material, Tabua is not a city in Portugal; rather, it refers to a polished tooth of a sperm whale that serves as an important cultural item in Fijian society. These items were traditionally used as gifts for atonement or esteem and played a significant role in negotiations between rival chiefs.
Historically, tabua were rare and obtained primarily from beached whales or trade with neighboring Tonga. They were often buried with the deceased alongside war clubs to assist them in the afterlife. During the early 19th century, the market expanded significantly as thousands of genuine teeth and fakes made from ivory and walrus tusks entered circulation, contributing to the development of the European art of scrimshaw.