请问:index finger(食指)这个词怎么来的啊?

由于时间因素,我就提供英文资料吧,暂且不帮你翻译了.
The index finger or forefinger is the second digit of a human hand,located between the thumb and the middle finger.It is usually the most dexterous finger of a hand and is usually used to point to things (a direction,an object etc.),thus it is also called the pointer finger.It is also called the second finger,index,digitus secundus,or digitus II in anatomy.The middle finger was called the index finger in earlier times,since it was usually the longest digit and was therefore used to flip through index cards.

果然跟我想的一样啊 .结合上面的英文,我给楼主用中文解释吧.
食指经常用于指东西,比如指着一样东西说,这是...,那是.,,,
这不就相当于指明序号吗?
index在英语中有个意思就是指南针的指针呢，.所以英语就用index finger了,有时也可以用point finger.后者就更加好理解了吧?:)...