Learn Polish: Zabiła go ciekawość.

You drop the adjective ending -y from ciekawy to get the stem ciekaw-, then add the suffix -ość. This suffix is the most common way to turn an adjective into an abstract noun in Polish, much like adding "-ness" or "-ity" to an English word.

Why does the verb zabiła have a feminine ending if it refers to killing a male?

The verb must agree with the subject doing the action, which is ciekawość (curiosity). A very helpful rule to remember is that all abstract nouns created with the -ość suffix are feminine. Because the subject is feminine, the past tense verb takes the feminine ending -ła.

Why is the subject ciekawość at the very end of the sentence?

Polish word order is flexible, and placing the subject at the end of the sentence is often used to build a tiny bit of suspense or to give the word more dramatic emphasis. You could say Ciekawość go zabiła, but the Verb-Object-Subject order here sounds much more punchy and idiomatic.

Why do we use the short pronoun go instead of jego?

We use the unstressed, short form go because the focus of the sentence is on the curiosity and the act of killing, not on the person who died. You would only use the long form jego if you wanted to emphasize that curiosity killed him specifically, as opposed to someone else.