Tam: யாழ்ப்பாணம் yāḻppāṇam – Sin: යාපනය yāpanaya

‘Town of the Lyre Minstrels’

From Tam: yal, ‘an ancient stringed musical instrument like a harp or lyre’; paan, ‘an ancient clan of minstrels who played the yal’; and Tam: pattinam , ‘a coastal town’.

This derivation, although somewhat contrived,  has a myth to go with it: a gift of land to a blind musician who particularly pleased the king, who then invited his fellow minstrels; and a handful of matching names with paan/pāṇ tacked on.

Also:

(1) ‘Java Town’   NP, Sri Lanka   [Tam: Yaalpanam/Yaalpanapattinam; Sin: Yaapanaya]. From Tam: Chava(ka), ‘Malay, Javanese (people)’; and pattinam , ‘a coastal town’. The ‘ch’ → ‘j’ → ’y’ sound shift in this solution and the one below is not uncommon, the ‘p’ to ‘f’ is also a possible sound change. In the 13thC Chandrabhanu, a Javanese ruler, conquered northern Sri Lanka and ruled Jaffna for thirty years. 

(2) ‘Pearl-fishery Town’  From Tam:  chalapam, ‘pearl-fishery’. The ‘ch’ → ‘j’ → ’y’ and  ‘p’ → ‘f’ , as above, all possible sound changes. Jaffna has long been a pearl fishing and processing region.

Prior to  the Civil War Jaffna was Sri Lanka’s second largest city. It is now 12th with a population of under 90,000 following expulsion, displacement and occupation.

The Jaffna or Aryachakravarti Kingdom ruled from around the city of Jaffna and  the Jaffna peninsula from the 13-17thC.

For related place names see Sri Lanka Place names.