Where does “இலண்டன்” come from?

இலண்டன் (Tamil) comes from English London, from Middle English London, from Old English Lunden, from Latin Londinium, from Proto-Celtic *Londinyom, from Proto-Indo-European lendʰ- — land, heath; loins.

Ancestry of “இலண்டன்”, step by step

Step	Language	Word	Meaning
1	English	London	Situated on the tidal River Thames in southeast England, with a metropolitan population of more than 13,000,000
2	Middle English	London	—
3	Old English	Lunden	London
4	Latin	Londinium	London
5	Proto-Celtic	*Londinyom	—
6	Proto-Indo-European	lendʰ-	land, heath; loins

Every word from Proto-Indo-European lendʰ- →Every word from Proto-Celtic *Londinyom →Every word from Latin Londinium →