This tradition was derived from the fact that a large meteorite had fallen from the sky into Ephesus. It apparently had a shape which the pagan leaders of Ephesus interpreted as a many-breasted female which they identified as an image of the goddess. Copies of this image thereafter became both commercially and religiously profitable to the Ephesians. Renaissance scholars denied that such an event could ever have happened until other meteorite falls began to be documented in modern times.

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