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。