He was a disciple of Agastya,who wrote Vedic Hymns,a scholar in Sanskrit,Agathyam ,Tamil Grammar,
Tholkaapiyar expresses his desire to streamline Tamil,
It is highly probable that he wrote Tholkaapiyam ,refining Aindhiram as it was becoming obsolete,disappearing.
Tamil Grammar Thokappiyam might be a refined,improved Aindhiram of Sanskrit Grammar.
And as Tholkappiyar’s Guru was a Scholar of Vedas,which is in Sanskrit, is it that Aindhiram is a Sanskrit Work?
Agastya could not have written Aindhiram in Tamil as the First Tamil Grammar Agathiyam was by Agastya,which has been lost?
Why write two books on the same subject?
Or ,as Agastya is a schloar in both Tamil and Sanskrit,Aindhiram could be in Tamil?