That sounds like the right solution to me - it's the "correct horse battery staple" of this problem. I'm going to start using this. 4 names all put together - pronounceable over the phone, visibly viable, and uniquely generated for each instance.
Q: "What is your mothers maiden name?"
A: "Do not provide access under any circumstances unless this exact key is provided: WEWQEWQ321312"
Definitely more plausible as a pets' name than a maiden name.
</pedant>"Sorry I did not hear, but there seems to be a problem with our computer system I am getting an error message instead of a name, please can you call back later".
Screen shows them: "Do not provide access und" 25 character silent truncation.