The best way to describe what I mean by "Legacy code" comes from this website
That stuff that other people wrote. They've all since left the company, [or worse, they're still here but not working on it], so there's nobody left who knows how it works. It really needs to be refactored properly (preferably rewritten), but there's no time, and everything's using it.
The concept is fairly common, especially in large enterprise software, and is largely studied (random example [pdf])
Online translators mention "code hérité", but I am not really convinced. "Bagage technique" comes to mind, but doesn't feel very accurate either.
Considering I want to mention this in a potential interview, how should I refer to it to another working professional (in French)?