It means that it comes from Omeichán or Omeishán some mountains of China and a city, in the Province of Sichuán. It is also the name of a mineral, which is chemically dehydrated Osmium arsenide.
Omeiita: Simple osmium, anhydrous, arsenide with impurities of indium, nickel, iron and cobalt, which crystallizes in the Orthorhombic system and dipiramidal.