To " counterfeit" currency means to make fake money or false money.

“伪造”货币的意思是制造假币或假币。

Back in the Civil War, in the mid part of the 19th century, there was a problem, at the end of the war in particular, with people counterfeiting U.S. currency.

回到南北战争， 在 19 世纪中叶，特别是在战争结束时， 人们伪造了美国货币。