So how did he adopt his last name as 'Nehru'?
There was a canal (Nahar) near by their house in Delhi, people started recognising them as Nehrus because of the NAHAR!

Part 1
— \u2728 (@Aamani_03) November 15, 2021
It's a bit lengthy, just keep reading :)
The British Nuclear Policy In The 1970s. https://t.co/DE1A7e1SQ0 pic.twitter.com/VSuUgpVMk6
"we don't negotiate salaries" really means "we'd prefer to negotiate massive signing bonuses and equity grants, but we'll negotiate salary if you REALLY insist" https://t.co/80k7nWAMoK
— Aditya Mukerjee, the Otterrific \U0001f3f3\ufe0f\u200d\U0001f308 (@chimeracoder) December 4, 2018