Hi, English isn’t my mother tongue so I was asking myself that question since I first encounted a w/… Back then I was like: “What tf does ‘w slash’ stand for?” And when I found out I was like “How, why, and is it any intuitive?” But I never dared to ask that until now
I learned similar shorthand from an accountant, who wrote transfer (money transfer between accounts) as tx.
Also, it used to be obligatory to put the dot on Mr., Mrs., Dr., etc. I’m old, I remember how it was taught. And we called those dots “periods”. I haven’t been in school in decades, but I’ve been noticing those dots disappearing.