Honestly just the word makes me giggle. I picture in my head little cartoon Grandmas with their skirts ballooning out around them as their fannies hit the ground.
I don’t know that I have anything deep or meaningful to say about plop. As I was sitting here thinking about it, I did think of the rain drops as it starts to rain… Those first gentle drops that says “rains coming”.
Or the saying “drop in a bucket” makes me think of plop… I can hear the drops of liquid plopping in the bucket.