The Free On-line Dictionary of Computing (19 January 2023):

Dragon Book

    The classic text "Compilers: Principles,
   Techniques and Tools", by Alfred V. Aho, Ravi Sethi, and
   Jeffrey D.  Ullman (Addison-Wesley 1986; ISBN 0-201-10088-6).
   So called because of the cover design featuring a dragon
   labelled "complexity of compiler design" and a knight bearing
   the lance "LALR parser generator" among his other trappings.
   This one is more specifically known as the "Red Dragon Book"
   (1986); an earlier edition, sans Sethi and titled "Principles
   Of Compiler Design" (Alfred V. Aho and Jeffrey D. Ullman;
   Addison-Wesley, 1977; ISBN 0-201-00022-9), was the "Green
   Dragon Book" (1977).  (Also "New Dragon Book", "Old Dragon
   Book".)  The horsed knight and the Green Dragon were warily
   eying each other at a distance; now the knight is typing
   (wearing gauntlets!) at a terminal showing a video-game
   representation of the Red Dragon's head while the rest of the
   beast extends back in normal space.

   See also book titles.

   (1996-12-03)


The Jargon File (version 4.4.7, 29 Dec 2003):

Dragon Book
 n.

    The classic text Compilers: Principles, Techniques and Tools, by Alfred V.
    Aho, Ravi Sethi, and Jeffrey D. Ullman (Addison-Wesley 1986; ISBN
    0-201-10088-6), so called because of the cover design featuring a dragon
    labeled ‘complexity of compiler design’ and a knight bearing the lance
    ‘LALR parser generator’ among his other trappings. This one is more
    specifically known as the ‘Red Dragon Book’ (1986); an earlier edition,
    sans Sethi and titled Principles Of Compiler Design (Alfred V. Aho and
    Jeffrey D. Ullman; Addison-Wesley, 1977; ISBN 0-201-00022-9), was the
    `‘reen Dragon Book’ (1977). (Also New Dragon Book, Old Dragon Book.) The
    horsed knight and the Green Dragon were warily eying each other at a
    distance; now the knight is typing (wearing gauntlets!) at a terminal
    showing a video-game representation of the Red Dragon's head while the rest
    of the beast extends back in normal space. See also book titles.