Caroline Floyd: I want to be grown-up and understanding about all this, I really do... I try so hard, but I can't. This won't bring those men back. You've been killing yourself over something you did, or something you didn't do right, and now you're looking for absolution... You know, you could get yourself killed.
Dr. Heywood Floyd: I'll be scared enough for both of us.
Dave Bowman: You see, something's going to happen. You must leave.
Heywood Floyd: What? What's going to happen?
Dave Bowman: Something wonderful.
Heywood Floyd: What?
Dave Bowman: I understand how you feel. You see, it's all very clear to me now. The whole thing. It's wonderful.
Tanya Kirbuk: You have been drinking your whiskey from Kentucky.
Answer: The most likely reason the name was changed was probably a literary one. It makes it easier for the audience to differentiate SAL from HAL, showing how they are two distinct computers playing different roles in the film. It may also just be a feminine nickname being that SAL has a female voice.
raywestI thought perhaps "SAL" was a nickname, also, until I saw that the computer's maker nameplate reads "SAL 9000" (visible in close-ups of SAL's glowing eye).
Charles Austin Miller