I did my Primary schooling in the UK, so when i came back to Aus and started High school I had a pommy accent, and of course copped grief for it.
Then one of the kids decided to say my name (Ashley) in as posh a voice as he could muster, it sort of came out as "Ooooshley", pretty quickly it was shorten to Oosh.
But instead of taking it as a tease, I actually kinda liked it, so adopted it as my nickname. After that I was always Oosh at high school, along with a few variations, Zoosh, Spoosh, Stoosh, etc.
It got continued at Uni, because one of my mates there was an Ash too, so i maintained Oosh to avoid confusion. I rarely even answered to Ash there.