A recursive acronym (or occasionally recursive initialism, and sometimes recursive backronym) is an abbreviation that refers to itself in the expression for which it stands. Due to the nature of the English language, which would infinitely recurse left-recursive phrases, recursive abbreviations are circular definitions.

In computing, an early tradition in the hacker community (especially at MIT) was to choose acronyms and abbreviations that referred humorously to themselves or to other abbreviations. Perhaps the earliest example in this context, from about 1977 or 1978, is TINT (”TINT Is Not TECO”), an editor for MagicSix. This inspired the two MIT Lisp Machine editors called EINE (”EINE Is Not Emacs“) and ZWEI (”ZWEI Was EINE Initially”). These were followed by Richard Stallman’s GNU (GNU’s not UNIX.) Many examples include negatives, such as denials that the thing defined is or resembles something.

Below is some interesting self describing acronyms:

• PHP — PHP: Hypertext Preprocessor (originally “Personal Home Page” tools, officially changed for PHP 3)^[3]
• PINE — PINE Is Not Elm, originally; PINE now officially stands for “Program for Internet News & E-mail”^[4]
• PNG — PNG’s Not GIF (graphics format, officially Portable Network Graphics)
• NINJA – Ninja Is Not Just Air.
• GNU — GNU’s Not Unix
• Cygnus — Cygnus, Your GNU Support
• RPM — RPM Package Manager (originally “Red Hat Package Manager”)
• YAML — YAML Ain’t Markup Language (initially “Yet Another Markup Language”)
• Zombie — Zombie-Oriented Machine-Being Interface Engine´

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