Here is an example from the play Othello.

 

These "key" words are not the most frequent words (which are those like the) but the words which are most unusually frequent in the Shakespeare play. Key words usually give a reasonably good clue to what the text is about.

 

 

Here the KWs show characters, themes. The word T is an abbreviation of it :

 

Per 100, 1000 or million?

In advanced settings you can display the % columns in different formats:

 

See also: word-lists with tags as prefix.