This is from the autobiography of Jack Black titled, You Can't Win.
"It is a corruption of "yekk," a word from one of the many dialects spoken in Chinatown, and it means beggar. When a hypo or beggar approached a Chinaman to ask for something to eat, he was greeted with the exclamation, "yekk man, yekk man"" ."

You Can't Win is a great story!