During the exodus from Italy Between 1892 and 1924, the Italian Government failed to send any identifying papers to the United States government indicating birth records, marriage records, etc., of these Italian boat people. (Among them were my loving grandparents.)
The USA detained this large group of Italians on Ellis Island until the paperwork arrived and the Italian citizens could be processed and admitted to this country, legally.
The Italian gov't never capitulated.
As the Ellis Island population grew, the US Government decided to allow the Italians entry into the country 'With Out Papers'.
Thus the term W.O.P.
Thus the reason it is exclusive to Italians.
Capice? Good.