OK

Online jargon, also known as text message shorthand, used in texting, online chat, instant messaging, email, blogs, and newsgroup postings, these types of abbreviations are also referred to as chat acronyms. 

Historical perspective: Young Boston intellectuals in the early 1800s used a humorous code of abbreviated phrases, like “KC,” or “knuff ced”; “KY,” “know yuse”; and “OW,” “oll wright.” And while most of them eventually fell out of fashion, one abbreviation persisted: “OK,” or “oll korrect.” All correct, a cousin of all right, was a common 19th-century affirmative that indicated everything was in order. Thanks to a series of lucky breaks, its jokey abbreviation, “OK” survived — and even ended up being (arguably) the first word spoken on the moon! - As seen on Vox.com