暗藏的动机的英文：
【美俚】the nigger in the fence; the nigger in the woodpile; a nigger in the fence

fence是什么意思：
n. 围墙，栅栏；障碍物；销赃犯
v. 用篱笆围住；防护；搪塞，支吾

The horse stopped short at the fence.
马跑到篱笆处突然停了下来。

The horse refused the first fence.
这匹马不肯跳过第一道栅栏。

That fence is the limit of the school.
那堵围墙是学校的界限。

woodpile是什么意思：
n. 柴堆;堆积的柴薪