I'm Irish and have never heard of Catholics going to Poland. The Catholic gentry who could afford it often had their children educated in France during the Penal Laws when education was forbidden to Catholics, but large scale emigration from Ireland only really kicked off in the nineteenth century and most people went to America and Australia. You might be confusing them with those earlier Irish who migrated to Europe during the seventeenth and eighteenth centuries. These were mostly soliders fighting in various foreign armies. For example in the early 17th century over a thousand Irish soldiers fought in the Polish-Muscovite wars but they did not remain in the Polish army and did not settle in Poland. By the way I love your username!