Hiraṇya disowned and prepared to destroy his own child for the sole act of reciting the divine name of the Lord. The Āzhvār, with great feeling, uses the tender word piLLai (son, child) to emphasize the cruelty of this act.
The natural affection a father feels for his child should render even the most ordinary words into a delightful melody.
Firstly, words spoken by a child in the student stage are inherently dear. Secondly, words spoken by one's own son should be uniquely sweet.
The commentary highlights the tragic depth of Hiraṇya's hatred for Sriman Nārāyaṇa, for it was a poison so potent that it transformed the sweet words of his own child into an insufferable torment.
āngu – "There."
Furthermore, it is a fundamental aspect of paternal love that a father should be able to lovingly tolerate anything his own child might say. Hiraṇya's reaction, therefore, was a violation of both societal reverence and paternal duty.
vāyil... – "From his mouth..."