incest

n. 近亲 * , *
【医】 近亲通婚

in.cest

n.（名词）
Sexual relations between persons who are so closely related that their marriage is illegal or forbidden by custom.
乱伦：血缘过近而使其婚姻不合法或为风俗所禁止的人之间的性关系
The statutory crime of sexual relations with such a near relative.
乱伦罪：与这样一个近亲发生性关系的法定乱伦罪

来源：
Middle English
中古英语
from Latin incestum [neuter of] incestus [impure, unchaste]
源自 拉丁语 incestum [] incestus的中性 [不纯洁的，不贞的]
in- [not] * see in-
in- [不] *参见 in-
castus [pure, chaste] * see kes-
castus [纯洁的，贞洁的] *参见 kes-