Where does “स्वास्नि” come from?

स्वास्नि (Nepali) comes from Sanskrit सुवासिनी — married woman.

स्वास्नि (Nepali): wife

Definitions

Step	Language	Word	Meaning
1	Sanskrit	सुवासिनी	married woman

स्वास्नि — Etymology, Origin & Word History | Etymology Explorer