For immigrants like me, who didn't grow up in the US, the "existing network" is largely absent / non-existent. So we always have difficulty trying to find co-founders as the people you can trust the most in your network are your "butt buddies" (in hindi we call them Chaddi-dost) and they are not here.
And most engineers, esp. technical engineers are introverts and do not like going to networking events.
My Hindi is far too limited to be sure, but I don't think that translation has the same connotation at all. Just fyi!
That said, just because I grew up in US and my butt buddies are here doesn’t mean they’re good cofounders. I’m regularly the only entrepreneurial person in my various friend groups.
Or, I suppose, 'BFF', but perhaps not even teenage girls can bring themselves to use that seriously today (I suspect it's 'so last year').
Not every engineer is an introvert, and cofounders need to wear multiple hats, so you're better getting a 75% engineer who is more versatile.
Attached at the hip is more like it. These are guys you grow up with and know their darkest secrets :)