betweenness (n.)

中古英语 bitwene，源自古英语 betweonum，麦西亚方言 betwinum，"在分隔的空间中，中途，在其中； 轮流地"，由 bi- "通过"（参见 by）+ tweonum "两个每个" 的复数形式 *tweon（比较哥特语 tweih-nai "两个每个"； 源自 PIE 词根 *dwo- "两个"）。

Between is literally applicable only to two objects; but it may be and commonly is used of more than two where they are spoken of distributively, or so that they can be thought of as divided into two parts or categories, or with reference to the action or being of each individually as compared with that of any other or all the others. When more than two objects are spoken of collectively or in divisibly, among is the proper word. [Century Dictionary]

Between 只能字面上适用于两个对象； 但通常情况下，它可以用于超过两个对象，前提是它们被分别讨论，或者可以将它们想象为分为两部分或两个类别，或者与每个对象的行为或存在相比较，而不是与其他对象或所有其他对象相比较。当涉及到集体或不可分割地讨论超过两个对象时， among 是正确的词语。[世纪词典]

In all senses, between has been from its earliest appearance, extended to more than two. [OED]

在所有意义上， between 从最早出现时就被扩展到超过两个对象。[OED]

Between a rock and a hard place "陷入困境，处于困难境地" 源自20世纪40年代，最初是牛仔俚语（早期是 between the beetle (hammer) and the block，19世纪末）。Between-whiles "间隔地" 源自17世纪70年代。

这是一个词缀，表示动作、品质或状态，附加在形容词或过去分词上，形成抽象名词，源自古英语 -nes(s)，来自原始日耳曼语 *in-assu-（同源词：古撒克逊语 -nissi，中古荷兰语 -nisse，荷兰语 -nis，古高地德语 -nissa，德语 -nis，哥特语 -inassus），来自 *-in-，最初属于名词词干，+ *-assu-，抽象名词后缀，可能源自与拉丁语 -tudo 相同的词根（见 -tude）。