Short answers, pulled from the story.
Koichi Ishii created the Chocobo in 1988 based on the memory of losing a pet chick he bought at a festival market during his elementary school years. The name was inspired by the Chocolate Ball confection created by Morinaga & Company, and the design was finalized in ten minutes during a lunch break.
The Chocobo first appeared in Final Fantasy II as a temporary mount despite initial rejection by series creator Hironobu Sakaguchi. It was relegated to a minor role in Final Fantasy II and III before becoming a central companion in Final Fantasy Adventure.
The Chocobo was originally envisioned as a non-vocal character communicating solely through movement to maintain an empathic connection. The iconic Kweh call eventually emerged to give the creature personality and became a defining feature of the species.
Boco was the first Chocobo portrayed as an individual character with a distinct personality in Final Fantasy V. Chocolina from Final Fantasy XIII was granted the ability to take human form by the Goddess Etro and became a merchant and quest giver.
The dedicated Chocobo spin-off series began in 1997 with Chocobo no Fushigi na Dungeon. This series spans nearly twenty entries across various game consoles and mobile platforms.