Kailayamreferred as Nodithanmalai in Thevaram. Only Srisailam referred as Thiru/Sree Parpadam.Parpadam is tamilization of the word Parvadam. Sri Sailam referred as Sri Parvadam in both Puranas and Bhudhist text. The other end of the srisailamrange is Nagrjuna Konda where Nagarjuna preached.
Parpadam to Parpan dose not have any proof.
Further if the brahmins who perform fire worship are from north. Then how come silappadikaram uses this word Parpandoing Fire worship?
There are many references to fire worship in Sangam Litarature, which has been discussed.
சாலி ஒருமீன் தகையாளைக் கோவலன் மாமுது பார்ப்பான் மறைவழி காட்டிடத் தீவலம் செய்வது
Puranaooru on Palyagasalai Peruvazhudi - His title itslef pal Yagasalai - one who did many havans. ஆவும், ஆனியற் பார்ப்பன மாக்களும், பெண்டிரும், பிணியுடை யீரும் பேணித் தென்புலம் வாழ்நர்க்கு அருங்கடன் இறுக்கும்
3. When temple worship gained equal importance like havans in Tamilnadu, a set of Brahmins took up the full time job in Tamilnadu. This hindered their daily muthee ( worshipof 3 fires daily) rituals. Brahmins duty is Aruthozhil - ( Shad karma) and taking up temple worship hinders that
1. Chanting Vedas 2. Teaching Vedas 3. Doing Yagams for welfare 4. Doing yagas for others 5. Taking alms for performing yagas 6. Giving that to poor during those yagas. as listed by Tholkappiyum.
In Purananooru Kouniyan Vinnandayan is praised for his yagams and donations. ( A sangam song on a vedic brahmin of Koundinya gothra)
Since full time temple duty hinders this, the separation came in tamilnadu.
That is why in North, the temple worship is open to all and brahmins are restricted only to rituals. In south the temple worship of both rituals and worship were taken by a set of brahmins and hence the separation.