This is the 4619th most frequent Polish word.
mieszkało
"Used to live" (past tense form of the verb "mieszkać").
Here, "mieszkało" refers to the past tense of "mieszkać," describing a group (siblings) living in a specific location.
W małym domku na skraju lasu mieszkało rodzeństwo.
In a small cottage on the edge of the forest lived siblings.
In this sentence, "mieszkało" conveys a historical fact about the occupation of a building by multiple families.
Przez lata w tej kamienicy mieszkało wiele rodzin.
For years, many families lived in this tenement.
"Mieszkało" is used here in an impersonal construction to indicate an unknown subject who lived in a place.