Italian-born navigator who served both Spain and Portugal. Mapmakers of the New Word used his name for these new lands

Amerigo Vespucci was an Italian-born navigator who served both Spain and Portugal and the one whose name was given by the mapmakers to the newly found lands.

Explanation:

Amerigo Vespucci carried out his voyage across the Atlantic Ocean and eventually reached the tip of the South American continent. It was only then that he and his fellow voyagers came to know that the land which the world earlier believed to be a part of Asia was a separate continent.

Christopher Columbus