A word/phrase for when an icon means something other than it's actual depiction [duplicate]

I am quite sure that there is a word for a symbol which was originated by a real-life, physical prototype but has since then outlived its origin.

Most notable example: the save button with floppy drive on it. Also, to a lesser degree, envelopes in email clients, and so on.

The "anachronism" or "metonymy" are close, but not exactly what I'm searching for.

Solution 1:

A skeuomorph is "a derivative object that retains ornamental design cues to a structure that was necessary in the original."

Solution 2:

Are you looking for "relic"? I appreciate that it can mean more than just a symbol.