Mark 14:36

Abba St Mark alone has preserved for us this word. St Peter could not fail to have treasured up the words of murmured anguish, which, "about a stone's throw" apart, he may have caught before he was overpowered with slumber. It is used only twice more in the New Testament, and both times by St Paul, Romans 8:15, "we have received the spirit of adoption, whereby we cry Abba, Father" and Galatians 4:6, "God hath sent forth the Spirit of his Son into your hearts, crying Abba, Father." In Syriac it is said to have been pronounced with a double bwhen applied to a spiritual father, with a single bwhen used in its natural sense. With the double letter at all events it has passed into the European languages, as an ecclesiastical term, -abbas," -abbot." See Canon Lightfoot on Galatians 4:6.

Father St Mark adds this probably to explain the Aramaic word, after his wont.