I’m not exactly sure.
I first encountered this word nearly one billion years ago, in an intensive summer-semester course in ancient Greek. (To say “first encountered” is a bit of a lie, since it implies I’ve encountered the word since. I haven’t, except from my own lips and fingers.)
One morning the professor got sidetracked by “psophos.” I remember he was trying to encourage someone (maybe anyone) to write and publish a paper on the word. He explained that psophos is translated as “a noise,” but is only used a handful of times in the literature that has been preserved: it was used in connection with the rustling of leaves and the light crunch of feet on gravel. He thought someone should gather up all these instances, reproduce the sounds, and try to narrow the definition beyond “a noise” to a particular kind of noise. Perhaps, he proposed, psophos is an onomatopoeia. In my mind, I can see him wandering the classroom whispering, “psophos,” while making strange hand gestures like Steve Martin in Roxanne regaling the clique of old ladies with a tale of aliens who wanted to do unspeakable things with mature women. This seems unlikely, but it is what I recall.
Google is no help, and I no longer own any Greek lexicons, so I can’t be sure if the definition of psophos in my memory is correct. But I’m happy to claim this word as my own.
Psophos is a noise, such as the rustling of leaves, crunching of gravel, or the clicking of keys on a laptop.