"Blighty" was first used in India in the 1800's, and meant an English or British visitor. It's thought to have derived from the Urdu word "vilāyatī" which meant foreign. The term then gained popularity during trench warfare in World War One, where "Blighty" was used affectionately to refer to Britain.

How did Blighty get its name?

The word derives from the Bengali word biletī, (older sources mention a regional Hindustani language but the use of b replacing v is found in Bengali and not Urdu) meaning "foreign", which more specifically came to mean "European", and "British; English" during the time of the British Raj.

What does copped a Blighty mean?

1.1 military slang A wound suffered by a soldier in World War I that was sufficiently serious to merit being shipped home to Britain. 'he had copped a Blighty and was on his way home'