How common is the practice of having a “veetu peru” which is wildly different from their actual name? And how did it become a thing?

I have friends from Chennai, whose homes I’ve visited to, over the years. And I’ve observed that in many cases, their families call them by a different name that is so different that you’d think they’re calling for someone else. Is this a Chennai/Tamil thing? I have friends from outside Chennai too and I’ve not observed this with them. Interestingly, many of the friends I observed this in, happen to be Brahmins, so I’m curious if there’s a caste aspect to this practice.