The kenosis theory states that Jesus gave up some of His divine attributes while He was a man here on earth. These attributes were omniscience, omnipresence.
In Christian theology, kenosis is the 'self-emptying' of one's own will and becoming entirely In this interpretation, Paul was not primarily putting forth a theory about God in this passage, rather he was using God's humility exhibited in the Etymology and definition · New Testament usage · In Christology · See also.
(1) "About the middle of the nineteenth century a new form of Christology made its appearance in the Kenotic theories." This is how Berkhof.