This came up once before on a forum somewhere, it may have been here, so I hope I give the same reason as last time!
It basically occured in Oman when I was in the forces. I have had a number of nicknames, the most obvious being Spam, most being based around my surname. I even liked some of them!
One of the guys decided that if i got a bit lonely in the desert, and if I was that way inclined (I'm not!), the offspring I would have from mating with a camel would be a Spamel! I think it was that or the gladiator night that decided that particular nickname.
The Squadron Bar was prepped for a gladiatorial night of fun and games, anybody not arriving in gladiator garb would be made to walk the slippery pole over a tank of water. So, our Troop got dressed up as gladiators, but not the Ridley Scott swords and spears type, no no! We went for the Wolf, Jet, and all the rest of them types, but we were all seriously lacking in looks and muscles!
We all got given tight shorts and vests bought from the Omani shops and naff gladiator names and mine was Spamel! None of us had to walk the pole apart from one, as he was an old fart and looked more like the guy who blows the whistle so that was who he went as! Not, strictly speaking, a gladiator!