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
Now that I know it though, it’s a good way to distinguish between similar common abbreviations. For instance I know you don’t mean “Actually” even though I’m not sure what you do mean by A11y.