Arthur Wellesley, 1st Duke of Wellington, (1 May 1769 – 14 September 1852) was a soldier and Tory politician statesman who was one of the leading military and political figures in his time. He was twice prime minister of the United Kingdom. He is among the commanders who won and ended the Napoleonic war when the coalition defeated Napoleon at the Battle of Waterloo in 1815. His grandfather, Richard Colley, adopted the surname Wesley, upon inheriting the estates of Mornington and Dangan in Co. Meath on the death of his cousin, Garret Wesley. This spelling was used for two generations, but Arthur's generation adopted the spelling Wellesley, which had been the family name anciently, as far back as the Norman era. This Anglo-Irish family had its roots in Somerset (the name being derived from the cathedral city of Wells) and had come to Ireland in the late 13th century.
Wellesley Avenue first appeared as a new street in 1867 and the name was approved 1869, originally spelt Wellesly Avenue (BCM, IHTA xvii, 39).