The acronym CAPTCHA, meaning Completely Automated Public Turing test to tell Computers and Humans Apart, could easily be condensed into a more memorable and shorter phrase. It is so long that it is its own word, and could be shortened to something like Test to Tell Humans from Computers, which shortens to a neat TTHC acronym.
I do not think that the CAPTCHA acronym needs to be shortened to anything else. Right now, this acronym is familiar to anyone who uses the Internet on a regular basis, and I have never heard one person in real life complain that it contains too many letters. Let's worry about something more important!
Captcha is one of the most annoying systems that I've ever had to deal with. I don't want anything more memorable from them, instead I want it completely dismantled so I can work without interruption. I don't know who came up with it but it is not an improvement for users, just an annoyance.
Its a two syllable word that's already easy to recall. Don't really see reason to change it. It's also essentially become a word on its own instead of just an acronym. I honestly have no idea what the letters of the acronym mean; and I'd guess most people don't either.