This is the 4362nd most frequent Polish word.
grzybów
"Grzybów" means "of mushrooms" (genitive plural form in Polish).
The word 'grzybów' is the plural genitive form of 'grzyb', used here to specify the found objects in a quantity expression.
Znaleziono wiele grzybów w lesie.
Many mushrooms were found in the forest.
'Grzybów' here is the plural genitive form of 'grzyb', indicating the ingredient source for the soup.
Babcia robi zupę z grzybów.
Grandma is making soup from mushrooms.
In this sentence, 'grzybów' represents a plural genitive case, used to describe mushrooms in terms of unfamiliarity or comparison.