Easton's Bible Dictionary

Abba - This Syriac or Chaldee word is found three times in the New Testament (Mark 14:36; Rom. 8:15; Gal. 4:6), and in each case is followed by its Greek equivalent, which is translated "father." It is a term expressing warm affection and filial confidence. It has no perfect equivalent in our language. It has passed into European languages as an ecclesiastical term, "abbot."