Original: The name "ABBA" is an acronym formed from the first letters of each of the group members' given names (Agnetha, Björn, Benny, Anni-Frid), and the group took this name officially in late 1973.
Simplified: The name "ABBA" is made from the first letter of each member's first name: Agnetha Fältskog Björn Ulvaeus Benny Andersson, and Anni-Frid Lyngstad.