Last name 盖西 (Gacy 
, 盖西 
) , around the world, is a very rare cognomen. The cognomen 盖西 is habitual in the United Kingdom, where it is a very rare surname, the United States, where it is an extremely rare surname, and Mexico. Measured by absolute frequency, it is the most numerous in China, the United States, and the United Kingdom. More prevalently, 盖西 is the forename as well as the last name.