Common belief is that SOS stands for “Save Our Ship” or “Save Our Souls” or “Stop Other Signals” or “Stomp Out Stupidity” or “Sale on Socks.” (Not really, I made those last two up.) In fact, SOS in not an acronym and it doesn’t represent anything at all.
Samuel Morse devised his telegraph code in 1835, using combinations of dots and dashes that he thought would be easy to memorize. The first distress signal was CQD, the “CQ” for a general notice that a message is coming, and “D” for “danger” or “distress.” However, this was cumbersome. In Morse Code, CQD was: -.-. –.- -..
So CQD was dropped.
In 1908, an international committee tried to come up with a distress signal that would be easy to remember during a crisis, and could be transmitted by an amateur with only rudimentary knowledge of Morse Code. They decided a simple combination of threes: three letters, each represented by three marks, since three is a universally favored number. Well, at least in Western cultures.
In Morse Code, the only letters represented by three identical marks are O (three dashes) and S (three dots). The committee toyed with OSO, but dashes are longer electrical signals to transmit than dots. An urgent message needed to be broadcast as quickly as possible and use as little power as possible, and so SOS became international standard.
During WWII, the signal “SSS” was adopted when the source of the emergency was a submarine attack, presumably so that potential rescue ships would know there was an enemy sub in the area.
In 1917, Edwin Cox of San Francisco dipped a small square steel-wool pad into a soap solution, and let it dry, and found this product sold well to housewives. His wife referred to the pads as “S.O.S.” for “Save Our Saucepans” believing (incorrectly) that the universal distress signal SOS meant “Save Our Ships.” Mr Cox took on S.O.S. (with the periods) as the name of his new product. The distress signal SOS has no periods in it, for obvious telegraphic reasons.
