Lo (Laughing out) was created as a consequence of Bloodlust80 forgetting to add the extra L in LoL. However since then, it has taken off as a legitimate phrase on the Internetz
Example of usage
person 1: I once said something crazy
person 2: Lo
Person 1: What are you doing right now?
Person 2: Browsing reddit
Person 1: Lo
"This is a funny article Lo"