The affix ṅīp is optionally used in the feminine after a prātipadika (Nominal Stem) ending with the word pād,
The word पाद becomes पाद् when final in certain Bahuvrihi compounds 5.4.140. Thus द्विपात् is both masculine and feminine, or it may optionally form its feminine by long ई (ङीप्). In the latter alternative, the form will be द्विपदी, the word पाद् being replaced by पद् by 6.4.130, (as read with 1.4.18). Similarly त्रिपात् or त्रिपदी; चतुष्पाद् or चतुष्पदी ॥,