The now extinct great auk of the North Atlantic was a large bird with small wings.
This made it very similar in appearance to the Antarctic penguin that we know today.
Because of these underdeveloped wings, the auk was called a “pin-wing”.
And so in 1578, when the first description of the bird came out of Newfoundland, it was written as it sounded in the local dialect.
Pin-wing became penguin.
The name and the spelling were then given to the auk’s southern look-alike.
Coincidentally, the auk’s Latin name is pinguinis.