Comparative evidence

i̯es

• OInd. yas-/yeṣ- 'be heated' (Whitney 1885: 130); 'froth up', 'foam'; 'heat one's self', 'exert one's self'; 'strive' (after) (MW: 849)

References

MW = Monier-Williams, M. 1899. A Sanskrit-English Dictionary. Clarendon Press.
Whitney 1885 = Whitney W. D. 1885. The roots, verb forms and primary derivatives of the Sanskrit language. A supplement to his Sanskrit grammar. Leipzig.