name for salt formerly much used in pharmacy and old chemistry, late 14c., from Old French sal, from Latin sal (genitive salis) "salt" (from PIE root *sal- "salt"). For sal ammoniac "ammonium chloride" (early 14c.), see ammonia. Sal volatile, "ammonium carbonate," especially as used in reviving persons who have fainted, is by 1650s, Modern Latin, literally "volatile salt" (see volatile).
updated on November 19, 2021