Ἀββά [1 verse](Hebrew word) "Abba" is abba, the Hebrew word for "father." -- "Abba" is uniquely used by Jesus here. It not a childish form of the word, but the Aramaic word used at the time to refer to "father," specifically one's own father. according to academics. The Hebrew term used in the OT is "ab," which was only used eight or nine  times to refer to God as the Father, such as in Isaiah 63:16,  Psalm 89:26. Isaiah uses the term most frequently, four times.