From Old Genovese ciüsma (from which Spanish chusma and Portuguese chusma descend), from Latin celeusma, from Ancient Greek κέλευσμα (kéleusma, “rhythmic chant to exhort rowers in galleys”), from κελεύω (keleúō, “to order, to bid, to exhort”).
Practice speaking and memorizing "ciurma" and many other words and sentences in Italian.