Green’s Dictionary of Slang

salty adj.

also saltyback
[? US navy jargon salty, tough, aggressive; Dillard suggests link to UK dial. salty, ‘of a bitch, maris appetens [desirous of a male]’ (EDD)]

1. [1920s+] (US) irritated, annoyed, feeling sour, supercilious.

2. [1920s+] (US, also salty-ass) tough, aggressive, used of a veteran of a particular environment, e.g. a prison.

3. [1920s+] (US teen) a general pej., unpleasant, uncouth, crude; of language, obscene.

4. [1980s+] of a garment, well-worn, ‘lived-in’.

In compounds

salty dog (n.) [dog n.2 ] (US black)

1. [late 19C–1930s] something or someone very exceptional.

2. [1970s] one who uses an excess of obscene language.