No source ties the dish's name or recipe to a single country of origin: the earliest documented recipe under a similar name is the 1891 Austrian Filet a la Wellington, the popular name points to the British Duke of Wellington with an unconfirmed connection, and food historians have also drawn French and Polish links.
What would resolve this A dated British source using the name Beef Wellington that predates or corroborates the 1891 Austrian recipe, or documented evidence directly connecting the dish to Arthur Wellesley, 1st Duke of Wellington.
OpenCulinary historyBeef Wellington (Wikipedia)