Question: The Australian cricket team toured Sri Lanka from 6 August to 20 September 2011, four uncapped players had been named in the Australian Test squad, including Shaun Edward Marsh, an Australian cricketer who plays for the Western Warriors in Australian domestic cricket and has represented Australia at Test, One Day International and Twenty20 International levels, and nicknamed SOS, an acronym of what ?
Sentence (from "Shaun Marsh"): Nicknamed SOS ("Son of Swampy"), he is a left-handed opening batsman and very occasional spin bowler.
Relevant evidence: Yes