Word History: from Latin index, indic- "forefinger, informer, sign", from in- "towards" + a second element related to dicere "say" or dicare "make known". The original sense "index finger" (with which one points), came to mean "pointer" (late 16th century), and figuratively something that serves to point to a fact or conclusion; hence a list of topics in a book ("pointing" to their location).
index case: [Medicine] the first identified case in a group of related cases of a particular disease.
正好也看到這樣一個例子，查閱了一些資料，我覺得應該是“第一例”或者類似於“首先”的意思。
從index的詞源來看，有指路、指明的意思。
Word History: from Latin index, indic- "forefinger, informer, sign", from in- "towards" + a second element related to dicere "say" or dicare "make known". The original sense "index finger" (with which one points), came to mean "pointer" (late 16th century), and figuratively something that serves to point to a fact or conclusion; hence a list of topics in a book ("pointing" to their location).
index case: [Medicine] the first identified case in a group of related cases of a particular disease.