According to Twitter founder Jack Dorsey, the company wanted a name that was reminiscent of what using the service was like. "When you received a tweet," Dorsey explained a few years back, "your phone would buzz. It would jitter. It would twitch."
Not a fan of either "jitter" or "twitch," Twitter employees took to the dictionary to look up potential alternates. Per the dictionary, a "twitter" is to make a consistent call of a light, quivery sound. As Dorsey recalls, he and his team felt that the word perfectly described Twitter usage – consistently making light communications. After originally spelling it Twttr, vowels were added to the name later on.