The Welsh phrase commonly cited as the origin of the English word “penguin” is pen gwyn.
Pen gwyn is usually translated as “white head,” from pen meaning “head” and gwyn meaning “white.” The proposed connection relates to the great auk, a now-extinct North Atlantic seabird that had prominent white markings on its head. Early European explorers later applied the name to southern birds that resembled the great auk in shape and habits.
The etymology is widely repeated, but historians have also proposed alternative explanations, including links to words associated with white or fat. The exact route by which the term entered English remains debated.
Modern penguins are unrelated to the great auk, despite the shared name and superficial resemblance. Great auks were alcids of the Northern Hemisphere; penguins are a separate seabird family native mainly to the Southern Hemisphere.