A transaction tax specifically relating to currency transactions is called a Tobin tax.
Sometimes it is called a robin hood tax, because it is supposed to target the rich and give to the poor. The problem with this analogy is that it is wrong.
Robin Hood was fictional, but he would steal off the rich, because the rich got rich by force, not by earning it. So in effect Robin Hood was only returning money back to its rightful owners. In the modern world, there are laws to stop rich people forcing money out of poor people. People hand over their money voluntarily by choice these days. Therefore there is no right to other peoples money.
In Robin hood the Sherif was the evil character, because he taxed the population too much and spent wastefully on banquets. Robin Hood was the good guy because he robbed the rich, which were closely aligned with the sherif at that time. Then supposedly he gave to the poor. What we have today is a merging of the Sherif and Robin Hood into one person. The government robs everyone, wastes on bureaucracy and gives a small portion to the poor. They can do what they want, because they always point to the robin hood aspect of their personality and say I am the good guy. But the sherif aspect is still there overtaxing/stealing and cowering behind the popular Robin Hood element.
More aptly the tax should be called a Sheriff of Nottingham tax. There are several reasons for this:
A Tobin tax would:
The Tobin tax was tried in Sweden 1984, and was a miserable failure, it was abolished in 1990.