[classicman]

Save Our Ship
Save Our Souls
Sink Or Swim

These are termed 'backronyms,' as explained below, and came into popular use AFTER SOS went into effect. In actuality, and as originally intended when SOS was introduced in 1908, the letters have no meaning.

SOS is a Morse "procedural signal” or "prosign." As the SOS signal is a ‘prosign’, its respective letters have no inherent meaning per se. In the simplest terms, SOS is a ‘SIGNAL’ indicating distress and the need for help, and not an acronym or abbreviation.

After SOS was first used by the steamship Arapahoe in 1909 (not the Titanic in 1912 as many people believe), people applied their own meanings to the letters. The most popular ones: "save our ship" and "save our souls." These are correctly termed ‘bacronyms.’

‘SOS’ was chosen because the three dots, three dashes, three dots are easy to transmit and not easily confused with other letters by the sender or recipients. With the advent of radios on ships beginning in the 1920s, ‘Mayday’ became, and still is, the International Distress Signal, but SOS served its purpose, for a while.