What is the root word for submit?

The root word for "submit" is "mittere", which is Latin for "to send".

The prefix "sub-" means "under" or "below". Therefore, "submit" literally means "to send under" or "to send below".

This makes sense when you think about the meaning of "submit" - it means to give in to someone or something else, effectively placing yourself "under" their authority or control.