For the tilde ~ symbol, there were several Urban Dictionary entries for it before 2008, such as “used at the end of words to make them longer” in 2007, but none of them mention sarcasm. The first time an Urban Dictionary entry mentioned sarcasm was in 2008 (giving the example “OMG that’s soo cool~”), followed by two more entries mentioning sarcasm in 2009. There’s our timeline. But for meaning, what’s interesting about the evolution of the ~sarcasm tilde~ was that you could figure it out without Urban Dictionary at all.
