The affix ḍhrak comes in the sense of a descendant after the word godhā,
Thus गोधा + ढ्रक् = गौधेरः ॥ Of the affix 'dhrak', the letter ढ् is replaced by एय् 7.1.2, क् causes Vriddhi 7.2.118 and makes the udatta accent fall on the final 4.1.165. Thus the real affix is एय्र, but the य् is elided by 6.1.66 and so the affix that is actually added is एर ॥
This word गोधा occurs in the Subhradi class (IV. I. 123), also, thus it takes the affix 'dhak' as well. Thus गौधेयः ॥,