tweet: Millennials use "lol" like STOP at the end of a telegram lol
tumblr response: REGRET TO INFORM YOU YOUR SON HAS DIED FROM TRENCH FOOT LOL HE SERVED WITH COURAGE AND HONOR LOL PLEASE ACCEPT OUR DEEPEST CONDOLENCES LOL
TL;DR an old form of communication (before and during WWI) where people used electrical signals and morse code to send messages to each other.