Shrēṣṭha ), is a common Newar

Newar

The Newa , Newār or Newāl) are the indigenous people and the creators of the historical civilization of Nepal's Kathmandu Valley. The valley and surrounding territory have been known from ancient times as Nepal Mandala, its limits ever changing through history.Newas have lived in the Kathmandu...

 surname . Shresthas traditionally have been predominantly traders. Since the unification of the country in the 19th century, with the opening up of the rest of the country for trading, Shresthas have migrated and settled down in various trade hubs all over Nepal, and the world.
Shresthas are a part of the Newar community of Kathmandu. As with all Newars, the mother tongue of Shresthas is Newari, or Nepal bhasa.