> I have avoided COBOL but I have seen stuff written in VB6/COM which was also in the same state. Eventually the one guy who knows anything about it leaves or dies. In the name of “progress” someone wraps it in something else and sticks a web API around it but everyone is afraid to touch that bit of VB code.

I call such things "Ancient Wonders". As in artifacts from long ago that the company owns, but nobody knows how they work or how they were built, and nobody can build one today. There may, in fact, be only one left. Whoever did build them was privy to some Tribal Knowledge that has since been lost.

I worked at a shop whose Ancient Wonder was their custom templating engine with an embedded Python interpreter. The only guy who knew how to compile it had left years before I joined, and as a result everybody just copied the same Solaris .so to new development/test/prod servers as they came in.