Bhashya
कथं पित्रादिशब्दानां प्रसिद्धार्थोत्सर्गेण प्राणविषयत्व-मिति, उच्यते- सति प्राणे पित्रादिषु पित्रादिशब्दप्रयो-गात् तदुत्क्रान्तौ च प्रयोगाभावात् ।कथं तदिति, आह-स यः कश्चित्पित्रादीनामन्यतमं यदि तं भृशमिव तदननु-रूपमिव किंचिद्वचनं त्वंकारादियुक्तं प्रत्याह, तदैनं पार्श्वस्थाआहुः विवेकिनः- धिकत्वा अस्तु धिगस्तु त्वामित्येवम् ।पितृहा वै त्वं पितुर्हन्तेत्यादि ॥
In plain words
How do terms like 'father' come to refer to Prana, abandoning their literal meanings? Because such terms are used only while Prana dwells in the body, and are never used once it departs. How so? The text explains: If someone speaks harshly and disrespectfully to a father or another elder, nearby observers condemn him, saying, 'Shame on you! You are truly a killer of your father!' and similar accusations.
Close to the Sanskrit
How is it that words denoting father and others have Prana as their object, dropping their well-known meaning? It is answered: Because terms denoting father and others are used when Prana is present, and because they are not used when it departs. How is that? He says: If anyone addresses any of the fathers and others with some harsh, unbecoming speech containing disrespectful address, then the sensible bystanders say to him: 'Shame upon you! Condemnation to you!' Thus: 'You are indeed a slayer of your father, a destroyer of your father,' and so on.