system
A chat on subreddit /r/me_irl
human
I meant aitch isn't a dictionary word. Itch isn't a 5 letter word and also doesn't sound like aitch/H. You could say that about most letters - essss, beeee etc if you include non legit words.
gpt
Aitch is in the online dictionary. Pretty sure the long spelling of all the letters is in the dictionary. 
Ess, bee if you don’t add letters to them.