The Sanskrit word ‘Puj’ and Tamil word ‘Pusai’ are considered cognate words.While in Sanskrit the word is a morpheme (vide page 641 of Sanskrit-English ,Dictionary-Monier Williams), in Tamil the word ‘Pusai’ breaks down into “Poo+sei’.’Poo’ is ‘flower’ and ‘Sei’ is ‘to do’.The ritual ceremony done with flowers to God , is thus called ‘Pusai’in Tamil.In contrast ‘Puj’ in Sanskrit means ‘to honour,to worship’and this inference has no basis. If cognate words in two languages X and Y are morphemes, the conclusion of cognation stands beyond question.But in case the word could be broken down further in X language, the probability of that word belonging to X language is certain.Hence the etymology of Sanskrit word 'Puja' is Tamil word 'Pusai' only.
The supporting collateral words in Tamil are 'Poosari'(Priest) ,Pookary(flower seller) ,Poopu(Puberty) ,Poo malai (flower garland) ,Poo chorithal(flower shower) etc.
Sanskrit does not have these supporting words.
