It's not what you think, it's certainly not what has been written. Nay, the origin of murlocs is more sinister than you could ever imagine. In fact, the true knowlege may even frighten the most hearty and couragous of you. But if you think you're ready for the truth, then read on.
It's widely believed that Murlocs are an ancient race of Azeroth, but of their origins little to nothing has ever been uncovered. Since their history has been primarily oral, and let's face it, nobody can really understand what they are saying, there has been nobody of knowledge to record their history in a more...permanent manner.
Very recently, however, in the rumblings of the earth prior to the Cataclysm, an ancient tablet has been uncovered (the first, but definately not the last) with writings relating to the ancient origin of Murlocs. It makes reference to a leader, presumably a king of their kind, named Norkostrider. Ancient names normally did were not fashioned by joining components of two separate names, but with the discovery of this name, and it being so old, the evidence is clear that Murlocs had origins with...Gnomes.
That's right, Gnomes are the progenitors of Murlocs. Many of us are familiar with the Gnome history, explained clearly over at wowwiki here, that talks about how Gnomes were first created as "mechagnomes" by the Titans, and later fell "victim" to the Curse of Flesh, thus making them a mortal, fleshy race. But with the Murlocs, the Curse of Flesh mutated. Unknown to all, even the Titans, one Gnome named Norko, being overcome with the Curse of Flesh, fled into the hills of Northern Kalimdor. His long journey there left him tired and weak, and in this weakened state the Curse began to mutate. Little by little the flesh that corruped Norko's body turned scaley and slimey. Horrified by the transformation, and feeling, in his words, "parched", Norko wandered east until he reached the shores of Azshara. There he took to the water, and there he stayed.
Unknown how Norko multiplied, within a hundred years there were already many clans of Murlocs set up all throughout Kalimdor. Norko changed his name to Norkostrider, for he strode along the beaches in search for his lost mind, or so they say, and became king of the first Murloc clan. Their own language there developed, but many believed Murlocs to be dumb, amphibious creatures only. The truth is that Murlocs retained the high intelligence of the mechagnome race, granted to them by the Titans when they were made to help shape the world. Today murlocs remain highly intelligent, albeit highly unintelligible.
Gnomes know nothing of their relationship with Murlocs in current Azeroth, for this knowledge had passed through the ages hidden from even the most wise and powerful. What can be wondered at now is how Murlocs will be treated as a species by their cousins. Will Gnomes, especially Mages and Rogues, continue to thrash and flame to death those that they once called brothers and sisters? Have Gnomes finally found the race of being capable of defeating without the assistance of 24 other, much larger, heroes of other, more noble races?
I feel for the Murlocs now, a pity that urges me to activism for the all-forgotten Gnome sub-species. They need a voice in the wilderness, preferably a voice that speaks English...er, Common tongue. Murloc matters must be of the utmost importance to the Gnome and Dwarf races, given this new information. Will they grant the Murlocs a place by their side in Ironforge or Gnomeregan?
Alas, the plight of the Murlocs is in the smallest hands in the world, and that's something to think about.