Debtor
A debtor was someone who owed money to another, a creditor. On Earth, those who did not pay their debts were sometimes imprisoned in debtor's prison. A welsher was a derogatory term for a debtor.

If it were not for the  Quinn, Isaac Newton would have become a debtor, suspected in several prostitute murders. ()

In an alternate timeline 1944, Sal described Joe Prazki as a welsher and a , adding that he was less than trustworthy. ()

In 2375, while praying, Quark described himself as the Blessed Exchequer's most devoted debtor. ()

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Illegal occupations