Pseud, the dictionary you cite covers British, not U.S. slang.

If the question is, "What does 'salty dog' mean in the Morris Bros. song?" I stick to my previous assertion: they've told us what they meant.

Obviously *no* ordinary word must have an essential meaning then, now, and forever.

Historically the term has had various meanings, none of them terrifically well known. Here are examples from primary sources that have nothing to do with the song. If all the meanings have anything in common, it seems to be an underlying idea that a "salty dog" is somebody or something that is special or otherwise remarkable.

The meaning "a sailor" (1914) seems to be a humorous extension.


J. F. Dobie, ed. Rainbow 'Round My Shoulder (Austin: Texas Folklore Society, 1927) 163 (written 1892):
My baby's a salty dog,/ My baby's a dandy,/ My baby's a vinegar pup,/ My baby's the candy.

Dallas Morning News (Apr. 13, 1906) 6:
Muskogee is a progressive city, It has taken to navigation early, and the siren shriek of the "Salty Dog" may be heard at any time bearing down the river with a party of gay and happy excursionists.

New Iberia [La.] Enterprise (July 28), 1906) 3:
SHERIFF'S SALE...FOR CASH....a certain gasoline engine boat named the Salty Dog.

Denver Star (July 18, 1914) 8:
Oh, Peaches and cream, you salty-dog. I am going to that Sunflower Dance at Fern Hall, Monday, July 20.

Fuel Oil Journal (December, 1914) 44:
THE TANK STRAPPER GEORGE SPEARY IS NOW A REGULAR SALTY DOG. John Tucker of the National Supply tells us that George Speary is now a regular navigator, having completed a full course in nautical science.

Bismarck Daily Tribune (July 20, 1916) 4:
Eagle Pass, Tex.--At "Dinty Moore's" they serve a brand new drink - the "salty dog"....It's a lime squashed in carbonated water, and served unsweetened with a cellar of salt.

Denver Post (Apr. 14, 1917) 5:
Jack Benton, better known to his friends as "Salty Dog," is now the popular cook at the Night and Day Cafe.

Charlotte Sunday Observer (Oct. 15, 1922) 8:
George Williams, alias "Salty Dog."

Journal of the House of the State of Missouri, Vol. 1) (1945) 372: Mr. Dent introduced S/Sgt. Jack ("Salty Dog") Welch to the House of Representatives.