The etymology is the same as the one that the modern slang 'chick' is from, that of old English 'brid', which meant 'young bird, chick, or in some cases, bird.' This word itself evolved from the Croatian term, bridd. Bridd became brid, and brid became burde. Burde referred to a young woman specifically, unless you were a Western Frisian. Then it meant beard. Another term, 'brȳd', was old English for bride. The words merged, and became byrde. Byrde eventually evolved into both the modern terms 'bride' and 'bird'. One of these terms, bird, was written on a note that was placed in a green glass bottle. The bottle, wary of its new inhabitant, rolled towards the sea. Upon entering the blue waters of the Atlantic ocean, it dove swiftly and deeply, striving to drive out the parasite within. But Bird was up to some fowl play. He clove the bottle asunder, hoping that he could ride the shock wave to the surface and out of the crushing depths. Little did he know that he was written on paper, and paper fibers do not stand up well to the waters of Earth. For a mere instant, he was dry, but then the terrible water flooded in, dousing every filament with wet, obliterating water. Crying to the heavens that were invisible to one as deep as he, he was filled with rage and shame for having destroyed himself. He came to rest, defeated, on the tomb of horrors that contained an elder god of great note.
Cthulhu lay dreaming, and the Quori preferred it that way. As horrific as they were, the dreams of Cthulhu were tasty. Cthulhu dreamed that a piece of paper fell on his tomb. That dream was eaten by the Quori. The Quori came to Sarlona. The Sarlonans came to Khorvaire. With them on their journey was Bird, given new life by time. Ragged and smudged, he was still legible, but only just. He had been placed in another bottle, a shiny blue vial that he shared with a scrap of papyrus with a drawing of a lizard on it. The human barbarian who was guarding the bottle, though, fell asleep as an earthquake shook his encampment. The rippling earth saw fit to throw Bird off the nearby sea cliff, where he floated for many long years. Nearly three millennia later, the bottle washed up upon the shores of Glamer Bay, where it was found and eaten by a giant river snake who had been playing in the delta of the Zilargo river. This snake would grow throughout several hundred more years until he was nearly the size of a dragon. He would then have his precious bottle (excreted mere years after its ingestion) stolen by a precocious Grippli rogue who wanted to see what was so shiny. The snake desired revenge, and he would have it cold. He hired a flight of silver dragons to help him track down the lawless thief, and they struck the grippli village at dawn the next day, freezing tree-houses and shattering them with their tails.
Seeing that their foes, who had been sleeping indoors, were but small tree frogs, the dragons decided to halt the destruction. Instead of a massed attack, they decided to hold a contest of martial prowess; one single dragon against the most powerful champion of the tribe. The grippli were at a loss. What hero could stand against an ancient silver dragon and live to tell the tale? The question was answered when an old (and bearded) tree frog burst out of the largest hut, twirling his nunchaku. It was the chief, Thor "Shark Emperor" Murray. Thor strode into battle against his foe, Bagogega the ice-breathing monstrosity. On the count of three, the fighting began.
Bagogega stomped the earth rapidly, but each time his talons descended upon the mighty Shark Emperor, the agile frogman would leap out of the way. Bagogega threw frozen shards of ice at the Shark Emperor, but the Shark Emperor would not stand still. Bagogega used his magicks against the Shark Emperor, but the Shark Emperor was impervious. Bagogega even used the ancient technique of the silver dragons: The Old Boulder Kick. The Shark Emperor could not see the boulder. The boulder was too high, and falling too fast. The boulder landed upon the Shark Emperor. The Shark Emperor was vanquished, or so it seemed. The boulder rose suddenly, the Shark Emperor beneath it. The Shark Emperor used his Forty Shivering Cascades Toss to toss the boulder high into the air. The Shark Emperor used his Meteor of the Five Plains to light the boulder on fire and toss it at Bagogega. Bagogega had no such powers. Bagogega had been vanquished by his own Boulder Kick, and the grippli were gladdened.
The Shark Emperor had won the combat. The Shark Emperor had beaten the dragons at the Destiny Stadium, and the grippli were the crowd, and the grippli went wild. The dragons fled, leaving the snake to slink home in defeat. The bottle was kept by the grippli forever more as a testament to the power of the Shark Emperor. The papers inside, however, were kept in written record alone, as their fibrous masses jarred against the shining beauty of the glass bottle. The grippli saw it as a sign that these new symbols, 'bird' and 'lizard' were together in their hour of triumph. This is why the Grippli see all dragons, and call them Bird.