Life as seen through my lens…
So, why "JohnK" and not "John"?
There are two reasons for this. In my first ‘proper’ job after school, I worked as a member of an 8 person team, and we had 4 Johns in the team. As a result, the first John (the manager) was just called John, and to differentiate between the remaining 3 johns, the first letter from the surname got tagged on. That also became my e-mail id (this is the second reason), and I was able to carry that ID into all of my subsequent jobs, so the name JohnK stuck.
In fact it’s stuck to a point where if I use my real name in a work conversation with someone I’ve just been introduced to but who I’ve exchanged e-mail with, I typically get the response "John who?" or a puzzled look, and then after a second or two, I get the follow-on comment "Oh… JohnK. So you’re JohnK!" and then they launch into a load of stuff that is usually too embarrassing to repeat (and usually but not always for good reasons)!
So I’ve become JohnK, or occasionally JK to everyone except my family (who only has one John to deal with – luckily for them)