When I worked at startups i interviewed people for swe jobs. I used to ask "what is your favorite 4 letter word?" and compare responses to their interview performance.
If someone asked me that question in an interview that would be a red flag for me.
It's a random classifier because it doesn't correlate in any way to any possible thing they could be doing as part of their job.
It's a magnet for potential bias because it's super-easy for the interviewer to deceive themselves into thinking they are gaining some insight about the candidate while they are actually just projecting their own feeling about whether they like the candidate or not.
Interviews can be stressful for interviewees. It might be tempting take it the opportunity to perform nonconsensual psychological experiments but just be kind and professional.
EDIT: In all seriousness, anyone have an idea of _what_ they're thinking when they ask this? I don't get it, at all. Yes it's a horrible interview question, but...what do they even think they're getting out of it?