This is Hacker News's fashionable way to refer to companies: not by their actual name but by their NASDAQ ticker name.
Seems pretentious as hell, to be honest.
It's what business newspapers do, especially online, as the name serves as a microformat causing the newspaper's CMS to automatically inject ticker information either on-hover or as an embedded aside.
Some ticker names have no relation to the company name though! You often have to go and look them up.
Cloudfare has 'NET' IIRC. Funny!
I'll have to admit I was also very confused by the use of 'FANG' so often around here.
FANG (or FAANG) isn't a ticker symbol though, just industry jargon.
FANG is the ticker symbol of Diamondback Energy, a Midland, Texas oil company.