As opposed to duke of any other British locale, that is. He was born in Dublin to Anglo-Irish parents and had no personal ties to Wellington that I can find.
It was IIRC chosen by his brother when he became a Viscount, as there already was a Viscount Wellselley obviously. He was in Spain at the time and had zero interest in the naming, so elder bro chose a town nearby.
[QUOTE=wiki]
His brother William selected the name Wellington for its similarity to the family surname of Wellesley, which derives from the village of Wellesley in Somerset, not far from that of Wellington.
[/quote]
I was surprised to learn a few years ago that the territorial designation doesn’t have to be a place in Britain or even the former Empire or current Commonwealth. After the First World War, Field Marshal French was named the First Earl of Ypres.
No Grantor of honours need consider geographical possession: the usurper Napoleon gave titles from places he had crushed thousands of miles apart. Duc’s of Istria, Dalmatia and Moscowa aren’t of French connection, and that bubble empire meant not of any duration beyond the pathetic.
The Wellesley name had been Wesley ten or twenty years before: they upgraded the spelling from nouveau-riche anxiety.
And yes, they were related to the gospellers.