Kautilya's Arthashastra 3.7.21

3.7.21

brāhmaṇasya vaiśyāyām ambaṣṭhaḥ, śūdrāyāṃ niṣādaḥ pāraśavo vā //

Sons begotten by Bráhmans or Kshatriyas on women of next lower caste (anantaráputráh) are called savarnas; but on women of castes lower by two grades are called asavarnas. (Of such asavarna sons), the son begotten by a Bráhman on a Vaisya woman is called Ambashtha; on a Súdra woman is called Nisháda or Párasava. The son begotten by a Kshatriya on a Súdra woman is known as Ugra; the son begotten by a Vaisya on a Súdra woman is no other than a Súdra. Sons begotten by men of impure life of any of the four castes on women of lower castes next to their own are called Vrátyas. The above kinds of sons are called anuloma, sons begotten by men of higher on women of lower castes.