What does the term Middle Ages come from?

Middle age is the period of age beyond young adulthood but before the onset of old age. Various attempts have been made to define this age, which is around the third quarter of the average life span of human beings.

According to Collins Dictionary, this is "... usually considered to occur approximately between the ages of 40 and 60".

The Oxford English Dictionary gives a similar definition but with a later start point "... the period between early adulthood and old age, usually considered as the years from about 45 to 65".