The explanation given on the Grammar Whisper website is a good one - if a bit over the top.

They use the phrase “Ask Me No Questions and I’ll Tell You No Lies” 

Their description goes ..." it may sound like a clever turn of words, but it holds timeless weight. It’s more than just an expression; it carries ethical undertones and speaks to the emotional distance people often create to feel safe. On the face of it, the line feels simple – “don’t ask, and I won’t lie” – but its real value lies in hiddenlayers. It means that when someone asks too much, they may uncover a truth that’s too inconvenient or even dangerous to handle. 

In quiet moments, folks use it to avoid confrontation or to withhold sensitive information. I’ve heard it whispered in a tense moviescene, and I’ve even said it half-jokingly, half-cautiously, when someone got too close to something I didn’t want to share.

That takes a bit of thinking about...