Before a taddhita affix having an indicatory ñ , ṇ or k the vṛddhi is substituted for the first vowels of both members of the compound which is the name of a city of the Eastern people and which ends in the word nagara,
As सोह्मनागरः (= सुह्मनगरे भवः), पौण्ड्रनागरः ॥ Why do we say 'of the Eastern people'? Observe माद्रनगरः, from मद्रनगरः the city of the Northern people.,