whittle down：削减；逐渐减少。
whittle：v. 削(木头)；削减。whittle away 切削。
【例句】
They are trying to whittle down our salaries.
他们正著手削减我们的薪水。
Their approach is to whittle away at the evidence to show reasonable doubt.
他们的做法是要削弱证据的说服力以提出合理的质疑。
