Last name Merlein (Merlein 
) , across the world, is a very rare surname. The family name Merlein is characteristic of Germany, where it is a very rare surname, Argentina, where it is an extremely rare surname, and Venezuela. Measured by absolute frequency, this name is the most popular in Germany, Argentina, and the United States. Very seldom, Merlein is the forename as well as the last name.