I heard this phrase for the first time yesterday.
Ironically, I'd just completed an item that will run later this week on Thanksgiving, Black Friday, Green Friday, Buy Nothing Day, Small Business Saturday and Cyber Monday.
Wasted Wednesday was a new one.
I figured it was called that as the day tends to be wasted, in productivity terms. And as a person who always works this day no matter what, and who often works at least one of the work days prior to the next business day (the infamous Cyber Monday), it is often not terribly productive.
But, nope. It's called that as apparently its a day in which there's a lot of heavy drinking.
I don't know what to say about that. Alcohol and the holidays have gone together for a long time. I suppose this is nothing new, but it sounds like it is. And if it is, that's a sad development.