It comes from the Latin word "medius", which also means "middle".
This root is found in many English words related to the middle, such as:
* Median: the middle value in a set of data.
* Medieval: relating to the Middle Ages.
* Medium: something that is in the middle, or a means of communication.
* Mediator: someone who acts as a go-between.
* Mediocre: of average quality, neither good nor bad.