The affix aṇ comes optionally after the word pīlā in denoting a descendant.,
The word पीला being the name of a female would have taken अण् by 4.1.113; but this अण् would have been prohibited by 4.1.121 as it is a dissyllabic feminine word. Hence the necessity of the present sutra. Thus पैलः or पैलेयः 'son of Pila.',