The term bozo bit has been used in two contexts. Initially a weak copy protection system in the 1980s Apple Macintosh Operating System, the term "flipping the bozo bit" was later reused to describe a decision to ignore a person's input. It is a whimsical term, possibly derived from the classic children's comedy character, Bozo the Clown.
Weak copy protection
In early versions of Apple's Macintosh Operating System, the "bozo bit" was one of the flags in the Finder Information Record (also called the "no copy" flag in some documentation), which described various file attributes. When the bit was set, the file could not be copied. It was called the bozo bit because it was copy protection so weak that only a bozo would think of it, and only a bozo would be deterred by it. After Mac System 4, introduced in early 1987, the Finder ignored this bit.
The cassette and ROM filing systems and the Advanced Disc Filing System  of Acorn MOS feature a rudimentary copy protection mechanism where a file with a certain flag set cannot be loaded except to execute it.
The Compact Disc has a similar "no copy" bit in the subcode, but nearly all disc-copying software ignores it, and usually removes it on copies. Consumer-grade dedicated hardware audio disc copiers usually honor the bozo bit, and will refuse to copy a disc with the bit set. Professional disc copiers ignore the bozo bit and will copy a protected disc.
Dismissing a person as not worth listening to
In his 1995 book Dynamics of Software Development (ISBN 1-55615-823-8), which presented a series of rules about the political and interpersonal forces that drive software development, Jim McCarthy applied the bozo bit notion to the realm of human interaction. The technical issues facing programmers were sufficiently daunting that just getting code written was commonly considered good enough; McCarthy and other authors (Lister & DeMarco, Constantine, McConnell) were just breaking the news that social issues trump technical ones on almost every project.
McCarthy's Rule #4 is "Don't Flip The Bozo Bit". McCarthy's advice was that everyone has something to contribute — it's easy and tempting, when someone ticks you off or is mistaken (or both), to simply disregard all their input in the future by setting the "bozo flag" to TRUE for that person. But by taking that lazy way out, you poison team interactions and cannot avail yourself of help from the "bozo" ever again.
- Chernicoff, Stephen (1987). Macintosh Revealed, Volume One: Unlocking the Toolbox. Indianapolis: Hayden Book Company. ISBN 0-672-48400-5.
- Stephen L. Michel (1988). IBM PC and Macintosh networking. Hayden Books. p. 10. ISBN 9780672484056.
- Bray, Andrew C.; Dickens, Adrian C.; Holmes, Mark A. (1983). The advanced user guide for the BBC Microcomputer (zipped PDF). Cambridge: Cambridge Microcomputer Centre. p. 347. ISBN 0-946827-00-1. Retrieved 19 April 2012.
- "5. The filing system commands". The Advanced Disc Filing System user guide (1st ed.). Acorn Computers. August 1985. p. 32. Retrieved 19 April 2012.
- Ronald J. Leach (2000). Introduction to software engineering. CRC Press. pp. 61–62. ISBN 9780849314452.
- Paul Glen and David H. Maister (2002). Leading geeks. John Wiley and Sons. p. 37. ISBN 9780787961480.