Learn Finnish: Tämä kaiverrettu koru on mahtava löytö. - This engraved piece of jewelry is an awesome find.

The word kaivertaa (to engrave) is a verb. To make its past passive participle, think of the regular passive past tense (kaiverrettiin) and replace the -iin ending with -u. This gives us kaiverrettu (engraved), which works just like a normal adjective in this sentence to describe the jewelry.

Why does kaiverrettu have a double 'r' when the basic verb is kaivertaa?

The verb kaivertaa undergoes consonant gradation when put into passive forms, where the strong rt changes to the weak rr. Because the past passive participle is built on the passive stem, it keeps that rr gradation.

If we were talking about multiple pieces of jewelry, how would kaiverrettu change?

Since kaiverrettu is being used as an adjective modifying koru, it has to match the noun's case and number. For a plural sentence, you would add the plural -t marker to the pronoun, the participle, and the noun: Nämä kaiverretut korut...

Is the word löytö (find) related to the verb löytää (to find)?