Prior to being named after the Marquis of Mancera the island was known as Güiguacabin (from ühueñn, "whistle", or ühua, "maize", and cahuin, "party") to the indigenous Mapuches. In his 1544 expedition Juan Bautista Pastene, made the island known for the Spanish and named it Imperial.
Before being designated after the Marquis of Mancera, the island was known as Güiguacabin among the local Mapuche people, who called it a place with a whistle-like sound or associated with maize and celebrations. It was during Juan Bautista Pastene's 1544 journey that he brought the island to the attention of the Spanish and subsequently named it Imperial.