What does it mean when a guy calls you 'boss' in a friendly way?

elatimer
This is a question out of curiosity not anything massively urgent.

I have a good guy friend of mine, who's recently within the last year or so, has started calling me 'boss' in way of greeting and high-fiving me, and wondered from a British point of view, if this means anything? Is a respectful thing?

Just to clarify, I probably only see him once a week in class and I don't nag him or anything, just joke around as usual and we tend to help each other out with work.

We had to work together last week and had to sit quite close together due to the lack of space around the computers and he didn't mind and then said, after we finished saying he quite enjoyed it and was looking forward to working with me in future so I imagine as close mates, he's just happy being close friends?

Thanks for your input! =)
Updates
+1 y
He's going away for the weekend and we're planning on having a catch up as we do, although admittedly we seem to be having more updates face to face over drinks, around uni than we used to, 2-3 since Sept. He's leaving this Friday at half 12 on the train and has asked me to meet up with him Friday at 11 on campus. Then today I saw him in between classes briefly, we talked for like 2-3 minutes and he briefly touched my shoulder at least 2-3 times in that space of time in front of my flatmate.
What does it mean when a guy calls you 'boss' in a friendly way?
2 Opinion