Where did perimeter come from and when?

Answer 1

Perimeter didn't 'come from' anywhere. The concept of 'how long is the bottom of the outside of this thing' has always existed. Perimeter is just the name for 'how long is the bottom of the outside of this thing'. As an example, the perimeter of any one of the pyramids has always been the same.

About 1600, the English word 'perimeter' was first used to describe 'the distance around the outside of stuff'

But, that distance was the same long before that!