Update: thank you everyone! user @Today has provided a great link of a discussion that suggests the correct answer is where being an abbreviation of, whereas as a replacement of since, hypothesized in these comments.
As I love archaic definitions, I’m more convinced to now that this is the answer!
Especially since the question originates from one weirdo using “where” instead of since.
https://english.stackexchange.com/questions/338694/is-it-ever-appropriate-to-use-where-instead-of-because-or-since
Like “Where we knew he was heading to Chicago tomorrow, we got on the first plane heading east to intercept.”
“Where we knew where the safe was, we began to cut through the wall in the corner behind her desk.”
Thanks
I’ve never heard them be interchangeable. Grew up in the NE US, PA, NY, FL, and MA.
I’ve spent most of the last twenty years in the Midwest, and can’t think of a single example.
The outlier would be very, very careful instructions - likely written - organized in an if/then fashion which is a totally different use case:
“Since” wouldn’t fit, at least without changing the instructions after the ellipsis.
And of course the classic example: “since you are up, get me a beer…” also doesn’t really work. (Apologies to some long irrelevant redneck comedian for ripping that off to make a point).
I’m trying in my head to make it fit in both casual and formal conversation, and it just won’t as far as I can tell.
Would love a counterfactual where both work!