The term 'Palindromic 'SOS' Pop Group' refers to the Swedish pop group ABBA. ABBA was formed in 1972 and is one of the most successful musical groups of all time, selling over 380 million records worldwide. The group's name is an acronym of the first letters of each of its members' first names: Agnetha, Björn, Benny, and Anni-Frid. The band is best known for their hit songs 'Dancing Queen, ' 'Mamma Mia, ' and 'SOS, ' which is a palindrome, meaning it reads the same forwards and backwards.