yajadhvainam is irregularly formed in the chandas (Vedas) for yajadhvanamenam,
The word यजध्वम् followed by एनम् loses its final म् in the Veda. As यजध्वैनं प्रियमेधाः (Rig VIII. 2. 37). The Kasika adds \that व is also irregularly changed into य\ : the form would then be यजध्यैनम् ॥ This is, however, a mistake as pointed out by Bhattoji Dikshit.,