Questions & Answers about Dlaczego zamurowali to małe okno?
How does the prefix za- interact with the root of zamurowali to mean "walled up"?
The root of this verb is mur (a brick or stone wall), which gives the base verb murować (to lay bricks or build a wall). Adding the prefix za- introduces the meaning of blocking, closing, or covering an opening. Together, zamurować means to close something off by building a wall over it.
Are there other common verbs that use za- in this exact same "blocking" way?
Why does zamurowali use the masculine personal ending -li if we don't know who "they" are?
When referring to an unspecified group of people (like generic workers, builders, or "the authorities"), Polish defaults to the masculine personal (virile) form. You would use the non-masculine -ły ending only if you were certain the group excluded adult human males.
To małe okno is the direct object here. Why didn't its endings change?
Direct objects take the accusative case, which often changes noun and adjective endings. However, okno is a neuter noun. In Polish, all neuter nouns and their modifiers (like to and małe) have the exact same form in the accusative case as they do in the nominative (dictionary) case.