This is the 13537th most frequent Polish word.
pieprz
Pepper.
Here, 'pieprz' is part of an informal phrase meaning to chatter or speak nonsensically.
Nie pieprz o rzeczach, na których się nie znasz.
Don't talk nonsense about things you don't know about.
In this usage, 'pieprz' refers to a spice commonly used in cooking.
Dodałem pieprz do zupy, żeby nadać jej ostrości.
I added pepper to the soup to make it spicy.
In this context, 'pieprz' again refers to the spice, but the historical perspective adds a cultural note about its value.