My full first name is Joshua, but when I was a kid everyone would just call me Josh. That was until 5th grade, when another Josh joined my class, and whose last name just happened to come right before mine in the roll call. I loathed that he "stole" my name and (in my head) made me sound like the repeat, so from that point on I decided that I would be Joshua because it sounded "fancier" to me. Years later, my choir teacher would sing that old "Joshua fought the battle of Jericho" song whenever he passed me in the hallways, which always made me laugh.
I've got a life long friend who's full first name is Josh, derived from the Japanese name Yosh. People often try to call him Joshua and it annoys the hell out of him.