feature mining

Adding features to software by finding them buried in an epically large code base. Typically sitting unused.

Fixing that error on the home page added a shiny graph.?
Where did that come from?
That code has been there for years?
Whoah that's some good feature mining.

instalegacy

Code created that becomes legacy code the moment it is written. Typically written by someone who has been allowed to code when they clearly shouldn't have been.

Woah! This new mobile-app code is instalegacy. Is that a GOTO?