I want to start with a little look at the etymology of the names Trinidad and Tobago, and more importantly, what the historical distinction is between the two islands.
That historical difference also shows up in different demographics – Tobagoans are largely of African descent alone, while Trinidad is more of a mix between Indian and African heritages.
Digging a little deeper into modern political structure, it’s interesting to note that Tobago, while electing MPs to the national Parliament, also has its own elected legislative assembly, the Tobago House of Assembly. It seems very similar to devolution in Britain, with Wales, Scotland, and Northern Ireland having their own assemblies for local matters but also electing MPs to London.
Tobago’s status inside the country is a live issue. Just this past year, a bill was put forward in the national Parliament to restructure the system to give Tobago self-governance. The bill is still at committee, and there has been a lot of debate by both Trinidadians and Tobagoans on the actual content of the proposal – what powers will it give Tobago, what will the national government be able to override, and just how independent Tobago will be.
Addendum: I asked the Trinidad and Tobago subreddit, and there’s consensus that the best way to refer to both islands at once / the country as a whole is Trinbagonian or Trinbagoan – as it includes Tobagoans, who are often overlooked if just called Trinidadian.