Jack Dorsey (@Jack), then an undergraduate student at New York University, introduced the idea of an individual using an SMS service to communicate with a small group. The original project code name for the service was twttr, inspired by Flickr and the five-character length of American SMS shortcodes.
The decision was also partly because the domain twitter.com was already in use, and it was six months after the launch of “twttr” that the crew purchased the domain and changed the name of the service to Twitter.
The developers initially considered "10958" as a short code, but later changed it to "40404" for "ease of use and memorability".
On Mar 21, 2006, when Jack Dorsey published the first Twitter message: "just setting up my twttr", has sold his first-ever tweet for more than $2.9M, donating the money to a charity battling Covid-19 in Africa.