How is “what is driving at” used?

In The Number 23 (2007), one line is: “What was driving you insane?”

Which movie is “what is driving at” from?

The clip at the top of this page is from The Number 23 (2007).

Idiom

the thing sb is trying to say

informal · Heard in 19 movies

what sb is driving at
the thing sb is trying to say
I wish I knew what they were driving at.

Definitions from the Oxford Advanced Learner's Dictionary, 9th edition

What was driving you insane?

Said in 8 films · #1