fgsfds (pronounced figgis-fiddis or F-G-S-F-D-S) is a saying used on imageboards and forums when a user finds the contents of the conversation ridiculous and wants to derail it. The seemingly random string of letters is allegedly meant to emulate someone slamming their left fist down on the keyboard.
According to Encyclopedia Dramatica and a 2006 post by user Reichu to Eva Geeks forum, the phrase came about when a 4chan user replied to a post with "fgsfds," after which another user named Oryan quickly photoshopped it onto an image of Harald Schmidt, a German talk show host, pointing upward (shown below).
4chan users began sharing the "fgsfds" image featuring Harald Schmidt around the site, leading to more variations using other images of people pointing up (examples shown below).
On August 23rd, 2005, yamz made a post to oneesmackk.blogspot.com mentioning that they're "obsessed" with fgsfds and posting a few examples of the meme, representing one of the earliest posts mentioning the term on the web (screenshot shown below).
Although no longer popular or common, new fgsfds posts continue to occasionally appear on the web. For example, on February 17th, 2020, /u/SelfDepricator uploaded a new version of the meme to /r/animemes (shown below, left). On December 17th, PastelMacroon posted an original "fgsfds" meme to DeviantArt (shown below, right).
 Eva Geeks – "you could either say "figgis-fiddis" or "F-G-S-F-D-S", but however you say it, it is the one word that makes no sense whatsoever at all …". Now commonly photoshopped onto pictures of anyone pointing their index finger in the air."