salvo n.

1719, an alteration of salva (1590s) "simultaneous discharge of guns, intended as a salute," from Italian salva "salute, volley" (French salve, 16c., is from Italian), from Latin salve "hail!," literally "be in good health!," the usual Roman greeting. It was regarded as the imperative of salvere "to be in good health," but it is properly the vocative of salvus "healthy" (from PIE root *sol- "whole, well-kept").

The notion is of important visitors greeted with a volley of gunfire into the air; the word was applied afterward to any concentrated fire from a number of guns, originally artillery pieces (of firearms by 18c.). As a verb by 1839. The same noun in the Latin sense, via Medieval Latin, came into English in senses common 17c.-18c. but archaic now: "a saving clause or provision; a solution or explanation; an expedient," etc.