TITLE: Tags for theorems, definitions, examples, etc. in monographs
QUESTION [9 upvotes]: I write many telegraphic reviews of monographs and textbooks.  
Occasionally I see certain books do something I think should become
an industry standard, namely tagging nearly every theorem, lemma, definition,
example, exercise, etc.  with some short mnemonic nickname, so readers need
not depend solely on a numbering scheme for cross-references, etc.
Examples of books that employ this laudable practice (and just happen to come to mind)
include 
  Epstein's Word Processing in Groups and 
  Thurston's Three-Dimensional Geometry and Topology.
My question: what author and/or publisher initiated this practice?  
(I'd like to cite the original source as a comparison when I feel the
visual design of a book makes it difficult for browsing.)

REPLY [6 votes]: First a comment. I recently wrote an intro level text on group representation theory with such tags. One of the reviewers found the tags annoying and said it seemed like I was sharing my latex labels with the world. I had to convince Springer to let me keep them. So it may be a matter of taste. 
To answer your question partially I doubt any publisher started this. I think it is an author thing. Notice both books you mentioned have Thurston and Silvio Levy involved.  My advisor tended to name theorems so that one could have something to refer to them by. I think many of his students picked this up. 
I doubt it originated with one person.