Topasses (Tupasses, Topas, Topaz) were a group of people led by the two power families — Da Costa and Hornay that resided in Oecussi and Flores.The Da Costa families were descendants of Portuguese Jewish merchants and Hornay were Dutch. Topasses were found in the various places of South Asia and Southeast Asia which were frequented by the Portuguese, such as Goa, Malacca and Batavia. In particular they are associated with the ethnically mixed Portuguese group that dominated politics on Timor in the 17th and 18th centuries.
The etymology of the name is obscure. It might come from the Tamil term tuppasi, "bilingual" or "interpreter". But it has also been associated with the Hindi word topi (hat) which refers to the characteristic hat worn by the men of this community as a marker of their cultural attachment to the European community. Hence, they are also referred to as gente de chapeo in Portuguese accounts or as gens à chapeau in French accounts. It partly overlapped with the Dutch concept mardijker, "free men", who also usually had a Portuguese cultural background, but had no European blood in their veins. While the mardijkers served under the Dutch colonial authorities, the Topasses of Timor were staunchly opposed to the Dutch and used the symbol of the King of Portugal as their ultimate authority.
As a political entity in the eastern part of Insular Southeast Asia, they arose with the Portuguese settlement on the small Island of Solor (from the 1560s), using Solor as a stepping-stone to the trade in sandalwood on Timor. When the Dutch East India Company conquered Solor in 1613, the Portuguese community moved to Larantuka on Flores. In spite of continuous hostilities with the Dutch, the Topasses managed to obtain a steady foothold on Timor after 1641, and part of the population of Larantuka moved over to West Timor in the late 1650s, as a response to the establishment of the VOC in Kupang in 1653. They were able to defeat Dutch military expeditions on Timor with the help of Timorese allies, in 1653, 1655, 1656 and 1657.