If one Googles, "So, how's by you?" a few references will show up, including this one:
I am old enough to remember the old black and white tv sitcom The Goldbergs, where Molly Picon, as Mrs. Goldberg, leaning on her elbows at her window to speak to a neighbor would ask, "So, how's by you?" This might have been a translation from the Yiddish, which is just a dialect of German.
There are influences on the language that many are not aware of. For example, the Eastern European syntax is the basis for the humorous phrase, "I threw my mother from the train a kiss."
It is also my opinion that the expression that seems to be omnipresent, "Oh my God!!!" was started by (you guessed it) the 1970's Jewish Princess. It became omnipresent in the vernacular maybe a decade or two later by mostly girls. It reminds me of how the bagel became a New York bread. OMG.
Anyway, "So" existed way before the 21st century, in a demographic far afield from where it is now used; perhaps overused?