A.T. Robertson Commentary Acts 4:36

"And Joseph, who by the apostles was surnamed Barnabas (which is, being interpreted, Son of exhortation), a Levite, a man of Cyprus by race," — Acts 4:36 (ASV)

Barnabas (Βαρναβας). His name was Joseph (correct text, and not Jesus) and he is mentioned as one illustration of those in verse 34 who selling brought the money. The apostles gave him the nickname Barnabas by which later he was known because of this noble deed. This fact argues that all did not actually sell, but were ready to do so if needed. Possibly Joseph had a larger estate than some others also. The meaning of the nickname is given by Luke as "son of consolation or exhortation" (υιος παρακλησεως). Doubtless his gifts as a preacher lay along this same line. Rackham thinks that the apostles gave him this name when he was recognized as a prophet. In Ac 11:23 the very word παρεκαλε (exhorted) is used of Barnabas up at Antioch. He is the type of preacher described by Paul in 1 Corinthians 14:3. Encouragement is the chief idea in παρακλησις though exhortation, comfort, consolation are used to render it (Acts 9:31; Acts 13:15; Acts 15:31). See also 16:9; 20:12. It is not necessary to think that the apostles coined the name Barnabas for Joseph which originally may have come from Βαρνεβους (Deissmann, Bible Studies, pp. 308-10), son of Nebo, or even the Hebrew Bar Nebi (son of a prophet). But, whatever the origin, the popular use is given by Luke. He was even called apostle along with Paul (Acts 14:14) in the broad sense of that word.