Around 1994, yes. W and L have been conversational terms for "a good thing happened" and "a bad thing happened" (a win or loss originally) since 2012 at the latest, but probably didn't become something almost everyone who speaks english would recognize until around 2015 or so. Its only become more popular since, and the terms originally come from labeling columns in competitive scoring (W/L/D, win loss draw) for games and matches for.... well centuries. The original meme phrase was 'add one to the win column' or any variation thereof, but eventually shortened to 'get a w' or 'take an l' situationally, and from there just became W and L without explanation because most people don't need it.
Edit: but I should clarify, shortening words to just one letter only became highly popular among the general population in 1994. More generally its been around for about 12000 years, and some examples can be seen sumerian and akkadian clay tablets written in cuneiform. It was 1994 when people started using pagers and the internet to commonly communicate and typing on them was even more of a hassle than caligraphy for the people of that time period, to whom computers and cellular phones were strange technology they were begrudgingly forced to use.
Winston Churchill is the first known user of OMG, in a telegraph, during WWII, (and the telegraph operator had to explain to the recipient that it meant oh my god). Other forms of shorthand have been in common use by stenographers for around as long as people have been using the latin alphabet. Most scribes copying manuscripts in the 1400s or so for example, would write 'a' in place of 'and' and many other similar single letter substitutions, and in fact this is the origin of the apostrophe, which literally means "there is supposed to be one or more letters in this word and I choose not to write them."
Before that we simply wrote Johns instead of John's (the apostrophe to denote possession is actually due to a centuries old uncorrected mistake that became the new correct).