Keep on and Plug away

Keep on verb - Allow to remain in a place or position or maintain a property or feature.

Plug away and keep on are semantically related in keep at topic. In some cases you can use "Plug away" instead a verb "Keep on", when it comes to topics like work hard at.

Plug away verb - Work doggedly or persistently.

Keep on and plug away are semantically related in keep at topic. You can use "Keep on" instead a verb "Plug away", if it concerns topics such as work hard at.