The verb "cut off" actually means "mutilate" or "castrate." The insistence of the Judaizers that the Gentile Christians be circumcised so disturbed Paul that he compared it to the practice of castration that some worshippers of a pagan goddess followed. Also, with bitter irony, he suggested that the Judaizers regress all the way into paganism instead of Judaism if they were going to trouble these new Christians in this way.

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8