Buttermilk is pretty sour and thick too. We always called whey what was left after straining the cheese.I think that was what buttermilk was at one point but I read somewhere that now they make it from milk and some sort of acidic additive. If I recall correctly, the stuff my grandmother gave us was pretty sour. We made butter with my gram as well but used her mixing stand not a churn. I thought the liquid left over from making butter was called whey too.
we made butter by shaking a jar with a thingy in it