Sin = Sinclair, my mother's maiden name.
Sull = Sullivan, my maiden name.
I was supposed to have been named Mary Sinclair Sullivan and have always regretted not being able to use Sin Sullivan. Mudcat and the Net solved the problem.
As my son has matured (thank God) he has come to terms with being adopted and loves to tease people who see a strong family resemblance. Also, he is half Iranian/half Hispanic. People never get the combo right.