After a word ending with a Patronymic affix the rule of affix in the sense of 'thence come' is like that relating to the affix denoting its mark.,
The word गोत्र in the sutra does not mean the technical Gotra of Grammar, but a descendant-denoting affix in general. The affixes denoting अङ्क are taught in 4.3.126 and 4.3.127. The affix वुञ् of 4.3.126 which comes after Gotra words, in the sense of 'this is his,' is refered to in this sutra, not merely the affix अण् of 4.3.127, denoting, 'this is his mark'.
Thus औपगवानामङ्कः = औपगवकः 'the mark belonging to the descendants of Upagu.' So also कापटवकः, नाडायनकः, चारायणकः ॥ The same words will also denote 'come there from' as औपगवेभ्य आगतम् = औपगवकम्, कापटवकम्, नाडायनकम्, चारायणकम् (formed by वुञ् 4.3.126).
Similarly बैदः, गार्गः, दाक्षः formed by अण् of 4.3.127 mean not only 'the mark belonging to the Vaidas, the Gargyas, the Dakshis,' but also that which comes from the Vaidas &c. The word यत् has the force of 'complete similarity,' as in कालेभ्यो भववत् 4.2.34, चरणेभ्यो धर्मवत् 4.2.46.,