Comparative evidence

1.ḱei̯

• OInd. śī 'lie' (Whitney 1885: 174); 'recline', 'rest', 'repose'; 'remain unused' (as soma); 'fall asleep', 'sleep' (MW: 1077)

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.