Albert Barnes Commentary Acts 15:39

"And there arose a sharp contention, so that they parted asunder one from the other, and Barnabas took Mark with him, and sailed away unto Cyprus;" — Acts 15:39 (ASV)

And the contention was so sharp. The word used here—paroxusmov—is that from which our word paroxysm is derived. It may denote any excitement of mind, and is used in a good sense in Hebrews 10:24. It here means, evidently, a violent altercation that resulted in their separation for a time, and in their engaging in different spheres of labour.