The phrase "one's original purpose" refers to the reason or intention for which something was created, established, or done in the first place. Full definition
The industrial - chic design pays homage to the building's original purpose as a pumping station. (visitphilly.com)
It is an ancient breed whose original purpose was a farm and hunting dog but has recently become more popular as a companion dog. (en.wikipedia.org)
Hopefully this will demonstrate just how diverse the traditional art form of silhouette cutting has become since it's original purpose as a substitute for the yet to be invented camera. (blog.feedspot.com)