"Abwehr" means "defense"--literally "fending off." "Fliegerabwehrkanone" literally means "aviator-fend-off-gun."
The Germans sometimes use the Latin/Greek/Syrian prefix "anti" (meaning "facing"), as in "Antialkoholiker" ("anti-alcohol activist" or "prohibitionist").
Wow. A complex language! It would appear to me then that as in the Romance languages the ‘’a’’ prefix denotes some kind of action in German? Like ‘’abstand(en)’’, stand back’’, ‘’antwort’’, ‘’answer’, ‘angriff’’, ‘’attack’’ and so on?