The affix yañ comes in the sense of a gotra (Patronymic) descendant after the words 1. kapiand 2. bodha when the special descendants of the family of aṅgirasa are meant.,
Thus कपि + यञ् = काप्यः 'the grand-son or a still lower descendant of 'Kapi' of the family of Angiras.' So also बौध्यः ॥
Why do we say of the family of Angiras ? Observe कापेयः (IV. I. 122) \the gotra-descendant of Kapi\ so also बौधिः formed by इञ् because it is a Non-Rishi word or because it belongs to Bahvadi 4.1.96 class.
The word कपि occurs in Gargadi class. The present sutra declares a restriction i. e. the 'yan' is to be applied only when Angirasa descendant is meant. It is included in the Gargadi class also for the purpose of applying (IV. I. 18). Thus काप्यायनी \grand-daughter or a still lower descendant of Kapi.\,