Montserratian means a person from Montserrat, or something that belongs to that island — food, music, a passport, a team. It is not the name of the island itself; the island is Montserrat. You add -ian, the same kind of ending as in Canadian. The place in the background is a small British island in the Caribbean (the Leeward Islands). Plymouth is still called the capital, but after the 1990s volcano many people left and the old capital was buried in ash, so the word now often points to a small population, including people who live overseas. You can use it as a noun (a Montserratian) or as an adjective (Montserratian families).