Adam Clarke on Mark 14:36

Abba, Father - This Syriac word, which intimates filial affection and respect, and parental tenderness, seems to have been used by our blessed Lord merely considered as man, to show his complete submission to his Father's will, and the tender affection which he was conscious his Father had for him, Abba, Syriac, is here joined to ὁ πατηρ, Greek, both signifying father; so St. Paul, Rom 8:15; Gal 4:6. The reason is, that from the time in which the Jews became conversant with the Greek language, by means of the Septuagint version and their commerce with the Roman and Greek provinces, they often intermingled Greek and Roman words with their own language. There is the fullest evidence of this fact in the earliest writings of the Jews; and they often add a word of the same meaning in Greek to their own term; such as מרי קירי, Mori, κυριε my Lord, Lord; פילי שער, pili, πυλη, shuar, gate, gate: and above, אבא, πατηρ, father, father: see several examples in Schoettgen. The words אבי and אבא appear to have been differently used among the Hebrews; the first Abbi, was a term of civil respect; the second, Abba, a term of filial affection. Hence, Abba, Abbi, as in the Syriac version in this place, may be considered as expressing, My Lord, my Father. And in this sense St. Paul is to be understood in the places referred to above. See Lightfoot.