The meaning "racy, sexy" is from 1866, from salt in the sense of "that which gives life or pungency" (1570s, originally in reference to words or wit); salt (adj.) also was used of lecherous (female) dogs, etc. (1540s) and also of persons (16c.-17c.).
The U.S. slang sense of "angry, irritated" is first attested 1938 (perhaps from similar use with regard to sailors, "tough, aggressive," which is attested by 1920), especially in phrase jump salty "unexpectedly become enraged" (1938). Related: Saltily.
updated on December 04, 2021