salvo (n.)
1719, alteration of salva (1590s) "simultaneous discharge of guns," from Italian salva "salute, volley" (French salve, 16c., is from Italian), from Latin salve "hail!," literally "be in good health!," the usual Roman greeting, regarded as imperative of salvere "to be in good health," but properly vocative of salvus "healthy" (see safe (adj.)). The notion is of important visitors greeted with a volley of gunfire into the air; applied afterward to any concentrated fire from guns.