The Aramaic word Abba (אַבָּא / Ἀββᾶ) means father — specifically in the intimate sense used by children addressing their dad. It was the common Aramaic word for father, used in everyday family speech. Jesus used it in His most anguished prayer: "Abba, Father, everything is possible for you. Take this cup from me" (Mark 14:36). Paul quotes it twice in the New Testament epistles (Romans 8:15; Galatians 4:6) to describe how believers, through the Spirit, cry out to God with the same intimacy Jesus had with the Father.
The word Abba is one of the most revolutionary terms in the entire biblical vocabulary. Jewish prayer addressed God in lofty, reverent terms — Adonai, Elohim, HaShem. But Jesus instructed His disciples to pray to God as "Our Father" (Matthew 6:9), and He Himself cried Abba in Gethsemane. This was not disrespect but rather the astonishing intimacy of the Son with the Father. Paul's theology of adoption (huiothesia, Romans 8:15) declares that through the Spirit of adoption, we receive the right to cry out Abba, Father — the same intimate access to God that Jesus Himself has. This single word, kept in Aramaic even in Greek texts, is preserved as a precious theological jewel: we are God's children, not merely His subjects.