Schaff's Bible Dictionary
FULLNESS. Gal 4:4. This expression has a peculiar meaning in some passages of the sacred writings. The "fulness of time," in relation to the Messiah, has the same meaning as the expression "when the measure of time was full" -that is, when the time had elapsed as appointed by God, and all the preparations for his coming were completed. So when the day of Pentecost was fully come. Acts 2:1. The same word is used, John 1:16 and Col 1:19, to signify the perfect and complete sufficiency of spiritual blessings in Christ Jesus.
"Fulness of the Godhead," Col 2:9, denotes all the attributes of the divine nature in their entire and complete perfection. The "fulness of Deity" was in Christ.