Where does “Anti-” come from?

Anti- (Portuguese) comes from Ancient Greek ἀντι-, from Ancient Greek ᾰ̓ντῐ́ — opposite.

Ancestry of “Anti-”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	ἀντι-	anti-, against; like, reminiscent of
2	Ancient Greek	ᾰ̓ντῐ́	opposite

Anti- — Etymology, Origin & Word History | Etymology Explorer