Learn Croatian: Otkud potječe ova starina? - Where does this old item originate from?

Yes, you can say Odakle potječe ova starina? Both otkud and odakle mean 'where from' and are generally interchangeable here when asking about the geographic or historical origin of something.

What is the infinitive of potječe, and how would I grammatically answer this question?

The infinitive is potjecati (to originate / to stem from). Because otkud asks 'from where', you would typically answer using the prepositions iz or od followed by the Genitive case. For example: Potječe iz Rima (It originates from Rome).

I know star means 'old'. Does the noun starina just mean 'an old thing'?

In this context, yes, starina refers to a physical antique, heirloom, or relic. However, it can also mean 'antiquity' as a historical time period. Using the demonstrative pronoun ova (this) makes it clear that we are pointing to a specific, tangible old item rather than an abstract era.

Why does the verb potječe come before the subject ova starina?

In Croatian questions introduced by an interrogative adverb like otkud, the verb typically comes immediately after the question word. This naturally pushes the subject (ova starina) to the end of the sentence.