"Avis Durgan" is the ASCII-string on which an exclusive OR operation (XOR) was performed in the text of the vintage Sierra Entertainment AGI adventure games to keep the gamers from snooping for clues in these games' resource files. In earlier versions of AGI games that booted directly from diskette, the "Avis Durgan" string was also used to encrypt sections of code as a copy-protection scheme.
The string "Avis Durgan" was chosen by the programmer of both uses, Jeff Stephenson, because it was the name of his then-girlfriend whom he met shortly before joining Sierra On-Line. As of 2009, they are still together, having been married in the 1980s.