The excerpt below is from Liar's Poker. What nationality does the word "nipper" refer to? Also, is it derogatory?
[...]he'd sell a few hundred millions worth of government bonds and grow bright again. “Yeah, Mikey!” he’d shout, as he scribbled a sales ticket. “The nippers, they love me. And I’m whipping and driving them. OOOOhhhhhhh yeaahhhh.”