The word originated wen a group of college students from the Bay Area went on a trip to Tahoe n were ASSED for 3 days strait. It came after the word ASSED was created, when one of the students used simple math and a little bravado to come up with the equation
SHITTED+ASSED=SHASSED. After a couple of sessions of Rumplestiltskinning (check definition by deggerkegger), the word SHASSED was officially created.
The word spread like an STI to the students respective colleges, rangin all da way from UCLA n USC 2 Yale n has finally made its way to urbandictionary, where da official definition is solidified 4 life.
"Hey bro, how SHASSED did that guy get when he got slapped in "How Can She Slap?""
"DUDE, HE WAS SHASSED OUT THE ASS!"
"Hey brohaminskeeter, is Reh Dogg SHASSED wen he makes his videos?"
"DUDE, HE IS ABSOLUTELY SHASSED IN THE TIT!"
"I JUST RUMPLESTILTSKINNED A 30 RACK OF KEYSTELOPE BY MYSELF AND NOW IM SHASSED!"