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
Well tbf those are post codes designed by the postal service to represent states. I wouldn’t really count it as a naturally developed abbreviation like the ones above, it’s no different from .fr, .es, .co.uk, etc.
The abbreviations for states used before the two-letter ones, however, are much weirder! E.g. Penna. for Pennsylvania
Tbf iirc the USPS had to make sure they didn’t conflict with other previously existing abbreviations. Although as someone living in LA, CA* they didn’t quite succeed
(Not Louisiana, Canada but the other one)