Power Fill is a custom name given to the unused powerup, as official text for the name was never made.
Power Fill Buttons

Power Fill is an unused powerup which was added in the Modern Day update. It is unknown what this powerup would have done, as it was never coded and only given 2 sprites. But it was most likely scrapped in favor of Power Shovel.

Description: N/A

Cost: N/A

Duration: N/A

Internal name: N/A