If you say that something is a leftover from a past period of time, you mean that it has its origin there and still exists even though most other things connected to that time have disappeared.
1. a small part or portion that remains after the main part no longer exists
Adjective
1. not used up;
"leftover meatloaf""she had a little money left over so she went to a movie""some odd dollars left""saved the remaining sandwiches for supper""unexpended provisions"
2. uneaten and saved for eating later;
"leftover food served at a later meal""yesterday's reheated soup"