Why is the inverted index called so and not simply index?

In my notes is represented like this:

From wikipedia:

In computer science, an inverted index (also referred to as a postings
file or inverted file) is a database index storing a mapping from
content, such as words or numbers, to its locations in a table, or in
a document or a set of documents.

Where is the inversion with respect to a normal index (like the one found at the end of books)?

Index: (in a book or set of books) an alphabetical list of names,
subjects, etc. with reference to the pages on which they are
mentioned.

Am I missing something? Like a nuance of the meaning of the name due to the fact that english is not my main language.

Here is an array:

• A[0] = Alice

• A[1] = Bob

• A[2] = Charlie

Here 0,1,2 are indices.

Now suppose that we want to know which index contains a given word. Then we use a dictionary:

• D[Alice] = 0

• D[Bob] = 1

• D[Charlie] = 2

This is an inverted index (according to your Wikipedia quote).

The word index has different meaning in different contexts:

• Technical books often have an index of terms at the end.

• The Catholic church held an index of forbidden books.

• In economics, there are financial indices.

• In computer science, an index is usually an integer used to index into an array.

StackExchange Computer Science Q#130814, answer score: 17