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.

index set un.變址組指標集；索引集；索引集合例句1.Firstly aimed at the establishment of risk models, the index set for model was confirmed.針對風險模型的建立進行建模指標集的確定。2.If the code always begins with the index set to zero, after processing, the index value will equal the number of parsed characters.如果程式碼常以設定為0的索引開始，處理後，索引值將等於解析過的字元的值。3.Below is the interactive version of the Shoe Thrower"s Index, set with the weightings we originally chose.下方是扔鞋者指數的互動版本，權重比是我們最初設定的。4.The results of case analysis showed that the credit index set was in line with the engineering practice, and the. . .例項分析的結果表明，信用指標的設定符合工程實際，模糊層次分析方法對實施施工企業的信用評價是可行的。5.INDUSTRIAL AUTOMATION. DATA EXCHANGE AND TRANSFER STANDARD SPECIFICATION. PART 2 : INDEX OF SET ENTITIES.工業自動化.資料交換和轉換標準規範.第2部分：規定組織的索引