After a prātipadika (Nominal Stem) which is the Ablative -5th case in construction, an affix (one of those already taught) comes in the sense of 'what appears for the first time'.,
The word ततः is understood in the sutra. The word प्रभवति means what manifests itself, or appears for the first time. Thus हिमवतः प्रभवति = हैमवती \The Haimavati\, a name of the Ganges, meaning 'which manifests itself for the first time or appears in the Snowy Range, its source being unknown'. So also दारदी \The Daradi\ i.e. the Indus appearing for the first time in Dardistan. The word प्रभवति has not the sense of उत्पत्ति, because that is included in तत्र जातः; it therefore means प्रकाशते, प्रथमतः उपलभ्यते, the source or origin being unknown.,