Παπάρι = vulgar slang for testicle.
-κτόνος = -cide, e.g. παιδοκτόνος = infanticide (the person), βασιλοκτόνος = regicide (still the person, not the act), εντομοκτόνο = insecticide (the product), ergo παπαροκτόνος, παπαροκτόνο = testiclicide :)
Still, not at all a common word in Greek. As I've...