Comment by boisterousness

It's the "Lava Flow" antipattern [1][2] identified by the Gang of Five [3], "characterized by the lava-like 'flows' of previous developmental versions strewn about the code landscape, but now hardened into a basalt-like, immovable, generally useless mass of code which no one can remember much if anything about.... these flows are often so complicated looking and spaghetti-like that they seem important but no one can really explain what they do or why they exist."

[1] http://antipatterns.com/lavaflow.htm

[2] https://en.wikipedia.org/wiki/Lava_flow_(programming)

[3] http://antipatterns.com/