Caerse con la lana / Soltar la sopa
To give money or information away reluctantly or unwillingly.
This idiom dates back to the middle ages when the kings tax collectors went home to home. The peasants would do almost anything to keep what little gold they had, which included swallowing the coins in effort to conceal them. It didn´t take long for the collectors to catch up on this act and forced the people to regurgitate the swallowed gold. whether it was by minute amounts of poison or just by sticking their fingers down their throats the collectors made the peasants “cough up” what was hidden. If you owed money to the mafia during the XX century in the USA, they would go and break your legs to make you pay. Some police forces used torture to make you confess what they wanted to know.
Example:•Johnny owes me $200 bucks but he keeps making excuses to pay. I will post on the net that he owes me and I will recommend everybody not to lend him any money. I think that way I can force him to cough up.