A word ending with a sixth case-affix is invariably compounded with a word ending with aka , when these affixes denote a sport or livelihood; and the compound is tat-puruṣa,
This is a Nitya-samasa incapable of analysis. This anuvritti of the word 'na' which began with sútra 10, does not extend further. The affix तृच् never has the sense of sporting or livelihood; the only examples possible are of 'aka.' Thus उद्दालकपुष्पभजिका 'a sort of game played by the people in the eastern districts in which uddalaka flowers are broken or crushed.' So also वारणपुष्पप्रचायिका 'a play of gathering flowers.'
So also दन्तलेखकः 'one who earns his bread by painting or marking the teeth.' नखलेखक 'a nail-painter by profession.'
Why do we say 'when meaning sporting or livelihood.' Observe ओदनस्य भोजकः.,