So it’s strange I hear it as a sound describing the action then?
I never thought of it as onomatopoeic before but, if I string the sound out – pooooooour – making the “o” noisy and its pitch rise slowly it does remind me of the sound of a cup being filled from a tap.
Ok, I still think it’s an unusual example but you’ve convinced me.
I retract my earlier comment and replace it with a “today I learned” for me. :)
“Pour over” is the sense you describe would be a metaphor.