The story goes like this: Frank co-signed a loan for a friend in Poland. Unfortunately, his friend turned out to be a poor risk and defaulted on the loan. This meant Frank now had to repay the loan.
Unable to make enough money working in Poland, Frank moved his family to America.
At the time everyone knew that America was "paved with streets of gold" or at least a land filled with more opportunity than Poland.
Frank got a job as an engineer and sent the money back to Poland.
He paid the loan back in full.