The affix ghañ comes after the verb śṛ 'to move' when the agent is permanently fixed.,
The word स्थिर means an object remaining steady throughout any period of time. That which thus remaining permanent moves through any interval of time, will apply to the agent of the verb. Thus, सृ + घञ् = सारः 'an essence'; as चन्दनसारः 'the essence of sandal', खदिरसारः 'the essence of catechu'.
Why do we say 'permanently fixed'? Observe सर्त्ता 'moves', सारकः 'that which flows'.
Vart:- The word so formed also applies to disease, fish and strength. As अतिसारः 'dysentery'; विसारः 'a fish'; सारः 'strength'.,