olemus
Wiktionary:
(computing) source code that relates to an obsolete operating system or other obsolete technology

ülevaateid
https://www.techopedia.com/definition/25326/legacy-code

https://en.wikipedia.org/wiki/Legacy_system

https://enkonix.com/blog/legacy-code/

https://hackernoon.com/an-essential-guide-to-legacy-code-no2337ml

https://events.drupal.org/sites/default/files/slides/refactoring_legacy_code.pdf

https://ptgmedia.pearsoncmg.com/images/9780131177055/samplepages/0131177052.pdf