Vestige
Etymology
From Latin vestigium, "footprint, track, trace," which is also the root of "investigate" (literally, to follow the footprints). The image is exact: a vestige is a footprint left by something that has walked on. English uses it for whatever residue of a former thing lingers into the present, including the biological "vestigial" organ.
noun · /VES-tij/
A small trace or remnant of something that no longer fully exists.
What it names
The word for the faint mark the past leaves behind — a vestige of an old wall, a vestige of a custom — the surviving sign of something largely gone.
Example
The hedgerow was the last vestige of a farm that had been swallowed by the suburbs decades earlier.
Related idea
Relic suggests something deliberately preserved and often valued; a vestige is an incidental leftover, a trace that merely happens to survive.