Answer by
eilrol (1431)
Agnetha Fältskog from Jonkoping Sweden, Bjorn Ulvaeus from Gothenburg Sweden, Benny Andersson from Stockholm Sweden, Anni-Frid "Frida" Lyngstad from Bjorkasen in Ballangen Norway. Hence, the A.B.B.A which is the first letter of the 4 members first name.