You don't always have to optimize for the right answer right away. Just asking someone who's worked with/on the codebase will often give you a jump start.
Presumably the code base didn't just have a single author (who is also no longer around). Git blame is amazing for not only tracking down who did what, but also seeing how the code base evolved.
You don't always have to optimize for the right answer right away. Just asking someone who's worked with/on the codebase will often give you a jump start.