Beside Vikings, it may be these guys https://en.wikipedia.org/wiki/Antillia

"an old Iberian legend, set during the Muslim conquest of Hispania c. 714. Seeking to flee from the Muslim conquerors, seven Christian Visigothic bishops embarked with their flocks on ships and set sail westwards into the Atlantic Ocean, eventually landing on an island (Antilha) where they founded seven settlements."