Blackmail 敲诈勒索
Blackmail (来源：英语学习门户网站2hzz.
com) 敲诈;勒索
practice blackmail
进行勒索
The word blackmail became popular in the 1800's and comes from the clan chieftains who ran protection rackets on farmers in Scottland.
If the farmers didn't pay the mail (an old term for rent), the chieftains would steal their cattle and crops.
Since this was considered evil, it was considered black.