Short form of Salvatore, from Latin salvator meaning 'savior.'
Sal is one of those names that wears its brevity like a badge of earned confidence. It operates most commonly as a nickname or short form for Sally (itself a pet form of Sarah, from the Hebrew "Sarah" meaning princess or noblewoman), for Salvador (from the Latin "salvator," meaning savior), or for Salvatore, the southern Italian elaboration of the same root. In this sense a single Sal might be tracing their name back to Jerusalem, Rome, or the Bay of Naples simultaneously, depending on the family tree.
In American literature, Sal Paradise — the narrator and barely disguised stand-in for Jack Kerouac in "On the Road" (1957) — gave the name its beatnik credentials: restless, open, searching, equally at home in a New Jersey diner and a Mexican cornfield. That association with the great mid-century American wandering gave Sal a worn-jeans cool that classier names could not manufacture. On the Italian-American side, Sal has long been a staple of the bocce court and the Sunday dinner table, the name that gets hollered across a backyard with complete affection.
In Britain, Sal carried a rougher, more working-class energy historically — a name from the market stalls and the music halls — though in the twenty-first century it has been reclaimed as a crisp, gender-flexible short form that feels both vintage and modern. As a standalone given name rather than a nickname, Sal has the advantage of all good short names: it is impossible to shorten further, ages without embarrassment, and fits any size of person.