special word zen practice

I heard about a practice the other day supposedly in zen where the meditator chooses a special word that they can repeat to themselves at any time that is meant to signal/point to some type of divine lesson that is trying to be taught to the meditator. The lesson isn't explicated specifically in any way, but there is just an understanding that there is one, mysterious though it may be.

The person who told me about this said they chose a really common word - "what".

It got me a little curious what that would do - you could choose an array of common words even, or just any common word, like it or that or this. Maybe it would be a little overwhelming but also maybe it would be very interesting

Hmm, not sure if I have enough info to understand what the practice is supposed to be.

But it reminded me of something I've heard a teacher suggest as a way to integrate mindful investigation with everyday life wherein you pick a common word and use it as a reminder to investigate that moment of your life in which you naturally utter it; it's just a reminder to be mindful basically and to consider your life contemplatively, like making a rule like every time you pass through a doorway to have a flash of awareness taking in your whole life in that moment. But you do it with a word.

Since every moment has the same 'truth' quality or true nature, any reminder can be a pointer at that, if we use that reminder to flash awareness on our actual life in that moment. I guess this depends on having had some insightful seeing of the nature of things prior to this in order for there to be something to be reminded of...