Why were American private investigators nicknamed 'Shamus'?

[Leda74]

Anyone know??

[Quizmonster]

When they emigrated to America, many Irishmen joined the police. Presumably, many became detectives and, later, private eyes. Seamas - pronounced shame-us - is a common Irish name, the equivalent of James. Another possible connection is from the Yiddish word 'shammes', meaning a sexton or caretaker. Put the two together and you've got some sort of 'Irish guardian'.