However it's spelled or pronounced, it means just what everyone said: "go f*** yourself!"
Derivation is from "a tan cul," or "up your ass." If my paisani here will forgive me for repeating a story I posted earlier:
I used to work for a very large corporation that had extensive grounds at their HQ location. They built a bocce court for employees to use on lunch hour. A league formed, and the finalists were a team of WASP middle managers vs a team of Italian-born groundskeepers. The WASPS won. I was the editor of the company newspaper and we had a column that included news of clubs that the company sponsored, including the bocce league. The captain of the WASP bocce team sent me a blurb on their victory. He called his team the "Fun Ghouls." I had to call this guy and tell him I couldn't run his blurb because his team's name was, in reality, an Italian obscenity that he and his teammates were unaware of. Was his face red!