Where does “Anti-Antifa” come from?

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

Ancestry of “Anti-Antifa”, step by step

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