The term 'Palindromic Pop Group' refers to the Swedish band ABBA, which is a four-letter palindrome. ABBA was one of the most successful pop groups of all time, having sold over 380 million records worldwide. They were active from 1972 to 1982 and are best known for their hit songs such as 'Dancing Queen', 'Mamma Mia', and 'Take a Chance on Me'. ABBA's music has been featured in numerous films, television shows, and musicals, and they remain one of the most iconic and beloved pop groups of all time.