FFS – For Fuck’s Sake.
The acronym is a part of internet jargon, like many other acronyms. This particular acronym probably evolved as a result of content moderation. With the censorship of profanity, it wasn’t possible to directly use the word “fuck.” and so acronyms and other forms of irregular language were developed. STFU, GTFO and WTF likely developed in the same way.
FFS is used to express extreme annoyance.
ffs, I lost my girlfriend last night.