The meaning of this name is self-evident. God is Lord of the earth just as much as He is God of heaven. He rules both domains and is sovereign over the inhabitants of both. This name is used of God in the book of Revelation.
Lord of the earth in Greek:
Ho Kyrios tēs gēs
Strong’s Concordance numbers: 2962, 1093
Bible reference: Rev. 11:4
These are the two olive trees and the two lampstands that stand before the Lord of the earth. (Revelation 11:4)
A similar name of God is found in the Old Testament: God of earth.