The forms bhayya and pravayya are found in the chandasa,
The word भय्य is derived from भी + यत्, and प्रवय्या from प्र + वी + यत् ॥ The guna ए is changed to अय् ॥ Thus भय्यं किलासीत् ॥ वत्सतरी प्रवय्या ॥ The यत् is added to भी with the force of Ablative by virtue of the diversity allowed by कृत्यलुटो बहुलं 3.3.113 ॥ Thus बिभेति अस्माद् = भय्यम् \frightening or fearable\. The word प्रवय्या is always used in the feminine: in other places प्रवेय is the proper form. Why do we say 'in the Vedas'? Observe भेयम्, प्रवेयम् in secular literature.
Vart:- The word हृदय्या should also be enumerated when referring to water. As हृदे भवा = हृदय्या आपः ॥ The affix यत् is added by 4.4.110 (हृदे + य = हृदय् + य) ॥,