If the latest version is the cutting edge or even bleeding edge, would a legacy version be a dull edge?
I've heard the term 'mechanical sympathy' for the ability to write efficient code due to understanding how a CPU works.
Is there a legacy software equivalent? 'Architecture sympathy', where you've worked out the structure that the author intended and things begin to make sense?
I really like the framing of legacy code as "money making code".
Presumably if it wasn't making money (possibly indirectly), it would have been deleted!