Upper/Upper-Middle Class Nicknames

[Slickly]

I grew up upper-working/lower-middle class, state educated, but we moved in Y5 and I went to a good grammar. I've spent the last 20 years in Australia. My DH is upper-working class, a lot of his uni friends went to prestigious public schools. We have just moved back and have seen a lot of DHs old friends. What is with the nicknames that have nothing to do with actual names, talking of names like Minky, Binky, Bunty, Berrie, Minty, Nixxy etc.
I met a grown woman who introduced herself as something similar to these, others were used on children/teens.
AIBU to think these are so cringeworthy? Why do they do this? Do you call yourself by a random unrelated nickname?
I know some small children who might go by a sweet nickname, but not teens or adults, I find it so odd!!

I don’t think either of you are “upper working class”.

most people who are working class don’t describe themselves as working class and if they do are proud to be working class.

there is no ‘upper’, just solidarity.

I recall a friend of a friend from years ago who was known as Hedge. Her siblings were known as Bag and Spank. They were definitely upper class. My DM knew 2 sisters at the private school where she worked who were known as Mitty and Tiggy.

I grew up with a nickname given to me by my Father. I’m not even sure if he remembered what my real name was! He was Irish and I asked what it meant and he said Mermaid. I found it quite odd as I really didn’t like swimming or the water. Years later I was telling my aunt and she laughed and told me it actually meant ‘bold child’ 😂 my DDs both have nicknames. They sign birthday cards with them, refer to themselves by them … they’re just pet names and I’ve always imagined that they’ll outgrow them. We also have theme tunes/fanfares that we hum when they arrive home 😂

There was a chap in our office, in 1980s, who was called Sting. He thought because people thought he looked like the pop star (he didn’t) it was because he looked like those weird under the sea people in Stingray.