गोष्पदं सेवितासेवितप्रमाणेषु

The word गोष्पद is formed by सुट् , when meaning a locality visited or not visited by cows, or when it means quantity.
Thus गोष्पदो देशः = गावः पद्यन्ते यस्मिन् देशे स गोभिः सेवितो देशः ॥ So also अगोष्पदान्यरण्यानि ॥ The word गोष्पद by itself does not mean 'not visited by cows'. Therefore the negative particle is added to give that sense. So also गोष्पदमात्रं क्षेत्रं, गोष्पदपूरं वृष्टो देवः ॥ Here the word has no reference to cow, but to the quantity of land and rain. When it has not the above senses, the form is गोपदम् = गोः पदम् ॥ What is the use of the word असेवित in the sutra, the word गोष्पद will give अगोष्पद by adding the negative particle, न गोष्पद = अगोष्पद? The force of नञ् compound is that of सदृश "like that but not that". As अब्राह्मण means "a man who is a Kshatriya &c. not a Brahmana, but does not mean a stone &c". Therefore अगोष्पद with नञ् would mean "a place like a pasture land but in which cows do not graze, but in which there is a possibility of cows grazing". But it is intended that it should refer to a place where there is no such possibility, hence असेवित is used. Therefore, deep forests where cows can never enter, are called अगोष्पद ॥