The affix ṭhak comes in the sense of 'whose habit is this' after a word in the Nominative 1st-Case in construction.,
Thus अपूपभक्षणं शीलमस्य = आपूपिकः 'one whose habit is to eat cakes'. Similarly शाष्कुलिकः, मौदकिकः ॥ The act of eating, and its habit are qualities understood in the sense of the affix.,