Where did the phrase plugging away originate?

The verb form of 'plug' meaning "to close tightly (a hole), to fill" is first recorded 1630. The phrase 'plug away' derives from naval bombardmental warfare, precise era unknown. In action, all effort was directed at sinking opponents until victory was (fairly) certain. Damage control was ignored until results were decisive. In a 'losing' battle, the enemy was welcome to try to save the ship, but, it was considered a minor victory of a sort when ones ship sunk, failing to fall into enemy hands. In a victory, once the enemy's defeat was certain, then, and only then, were hands released from their aggressive responsibilities to repair standing and running rigging, haul the wounded below and begin damage control and 'plug away' any underwater shot holes.