Air carrier Maintenance personnel reported undeclared dry ice being loaded. Dry ice was removed prior to departure.

Narrative

I was working flight ABCD ZZZ on [Gate] X as crew chief; before the loading process I check if there any DG plan for this flight ABCD to ZZZ; but I did not see any listed for this flight. During the loading process I scan two boxes containing Dry ice with the label un3373 and the class 9 division label on it in the scanner I press the important package option for hazmat. I notified the captain about the DG is not planned for this flight and he told me that he was going to check on it. I double checked with him; and he said that he is still checking on it. I was waiting for the captain to see if everything is good to go or I had to remove the boxes. All this conversation happened to the gate before he was authorized by the tower to push the aircraft. While I was waiting to find out from the captain if I was needed to remove the boxes from the aircraft prior to be push from the gate I thought that the captain received the ok from dispatch. aircraft did not take off from ZZZ1 it return to another gate to remove danger good from aircraftIn futures Dry Ice DG they should eliminate UN 3373 because that create confusion if DG notification is required or not.